Day 7

* Programs may start at non-zero instructions
 * Input uses mutable VecDeques and consumes values as they are encountered
 * Output uses a mutable vector, and multiple outputs will be pushed on it
 * If no value is present in the input queue, the program blocks on input
 returning the status Status::WaitingForInput and the instruction to resume
 the program from.

day7/Cargo.lock

@@ -0,0 +1,30 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day7"
+version = "0.1.0"
+dependencies = [
+ "icc",
+ "itertools",
+]
+
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
+[[package]]
+name = "icc"
+version = "1.0.0"
+
+[[package]]
+name = "itertools"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+dependencies = [
+ "either",
+]

day7/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "day7"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+icc = { path = "../icc", version = "1.0.0"}
+itertools = "0.10.3"

day7/src/#main.rs#

@@ -0,0 +1,132 @@
+use std::collections::VecDeque;
+use itertools::Itertools;
+
+fn main() {
+    let program = vec![3,8,1001,8,10,8,105,1,0,0,21,38,63,88,97,118,199,280,361,442,99999,3,9,1002,9,3,9,101,2,9,9,1002,9,4,9,4,9,99,3,9,101,3,9,9,102,5,9,9,101,3,9,9,1002,9,3,9,101,3,9,9,4,9,99,3,9,1002,9,2,9,1001,9,3,9,102,3,9,9,101,2,9,9,1002,9,4,9,4,9,99,3,9,102,2,9,9,4,9,99,3,9,102,4,9,9,101,5,9,9,102,2,9,9,101,5,9,9,4,9,99,3,9,1002,9,2,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,101,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,99,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,1001,9,2,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,1,9,4,9,99,3,9,1002,9,2,9,4,9,3,9,1002,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,1,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,99,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1002,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,1,9,9,4,9,99,3,9,101,1,9,9,4,9,3,9,101,1,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,99];
+
+    let mut max_storage = 0;
+    let mut max_settings: Vec<i32> = Vec::new();
+
+    {
+        let settings = vec![0, 1, 2, 3, 4];
+        // Cheese.
+        for permutation in settings.into_iter().permutations(5) {
+            //println!("{:?}", permutation);
+            let storage = run_amplifiers(&program, permutation.clone());
+            if storage > max_storage {
+                max_storage = storage;
+                max_settings = permutation.clone();
+            }
+        }
+        println!("[Part 1] Settings {:?} produced a value of {}", max_settings, max_storage);
+    }
+
+    {
+        let settings = vec![5, 6, 7, 8, 9];
+        for permutation in settings.into_iter().permutations(5) {
+            let storage = run_feedback_amplifiers(&program, permutation.clone());
+            if storage > max_storage {
+                max_storage = storage;
+                max_settings = permutation.clone();
+            }
+        }
+        println!("[Part 2] Settings {:?} produced a value of {}", max_settings, max_storage);
+    }
+}
+
+fn run_amplifiers(program: &Vec<i32>, settings: Vec<i32>) -> i32 {
+    let mut storage: i32 = 0;
+    for setting in settings {
+        let mut input = VecDeque::from([setting, storage]);
+        let mut output: Vec<i32> = Vec::new();
+        icc::simulate(&mut program.clone(), &mut input, &mut output, 0);
+        storage = output[0];
+    }
+    return storage;
+}
+
+fn run_feedback_amplifiers(program: &Vec<i32>, settings: Vec<i32>) -> i32 {
+    let amplifiers = [
+        // program, input signal, entrypoint, setting
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+    ];
+    let mut iter: i32 = 0;
+    loop {
+        for (index, setting) in settings.iter().enumerate() {
+            match amplifiers[index].3 {
+                icc::Status::Finished => {
+                    if index == 4 {
+                        // the output of amplifier 4 is stored on the input of amplifier 0
+                        return *amplifiers[0].1;
+                    }
+                    continue;
+                },
+                _ => {}
+            }
+            println!("[Iter {}] Running amplifier {} from instruction {}", iter, index, *amplifiers[index].2);
+            let mut input = if iter == 0 {
+                VecDeque::from([*setting, *amplifiers[index].1])
+            } else {
+                VecDeque::from([*amplifiers[index].1])
+            };
+            let mut output: Vec<i32> = Vec::new();
+            let result = icc::simulate(amplifiers[index].0, &mut input, &mut output, *amplifiers[index].2);
+            match result.status {
+                icc::Status::WaitingForInput => {
+                    println!("[Iter {}] Amplifier {} is waiting for input", iter, index);
+                },
+                _ => {},
+            }
+            let amp_index = (index+1) % settings.len();
+            *amplifiers[amp_index].1 = output[0];
+            println!("[Iter {}] Amplifier {}->{}: {}", iter, index, amp_index, output[0]);
+            *amplifiers[index].2 = result.instruction;
+            *amplifiers[index].3 = result.status;
+        }
+        iter += 1;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_1() {
+        let program = vec![3,15,3,16,1002,16,10,16,1,16,15,15,4,15,99,0,0];
+        let settings = vec![4, 3, 2, 1, 0];
+        assert_eq!(run_amplifiers(&program, settings), 43210);
+    }
+
+    #[test]
+    fn example_2() {
+        let program = vec![3,23,3,24,1002,24,10,24,1002,23,-1,23,101,5,23,23,1,24,23,23,4,23,99,0,0];
+        let settings = vec![0,1,2,3,4];
+        assert_eq!(run_amplifiers(&program, settings), 54321);
+    }
+
+    #[test]
+    fn example_3() {
+        let program = vec![3,31,3,32,1002,32,10,32,1001,31,-2,31,1007,31,0,33,1002,33,7,33,1,33,31,31,1,32,31,31,4,31,99,0,0,0];
+        let settings = vec![1,0,4,3,2];
+        assert_eq!(run_amplifiers(&program, settings), 65210);
+    }
+
+    #[test]
+    fn part2_example_1() {
+        let program = vec![3,26,1001,26,-4,26,3,27,1002,27,2,27,1,27,26,27,4,27,1001,28,-1,28,1005,28,6,99,0,0,5];
+        let settings = vec![9,8,7,6,5];
+        assert_eq!(run_feedback_amplifiers(&program, settings), 139629729);
+    }
+
+    #[test]
+    fn part2_example_2() {
+        let program = vec![3,52,1001,52,-5,52,3,53,1,52,56,54,1007,54,5,55,1005,55,26,1001,54,-5,54,1105,1,12,1,53,54,53,1008,54,0,55,1001,55,1,55,2,53,55,53,4,53,1001,56,-1,56,1005,56,6,99,0,0,0,0,10];
+        let settings = vec![9,7,8,5,6];
+        assert_eq!(run_feedback_amplifiers(&program, settings), 18216);
+    }
+}

day7/src/.#main.rs

@@ -0,0 +1 @@
+kienan@monolith.244424:1652264161

day7/src/main.rs

@@ -0,0 +1,132 @@
+use std::collections::VecDeque;
+use itertools::Itertools;
+
+fn main() {
+    let program = vec![3,8,1001,8,10,8,105,1,0,0,21,38,63,88,97,118,199,280,361,442,99999,3,9,1002,9,3,9,101,2,9,9,1002,9,4,9,4,9,99,3,9,101,3,9,9,102,5,9,9,101,3,9,9,1002,9,3,9,101,3,9,9,4,9,99,3,9,1002,9,2,9,1001,9,3,9,102,3,9,9,101,2,9,9,1002,9,4,9,4,9,99,3,9,102,2,9,9,4,9,99,3,9,102,4,9,9,101,5,9,9,102,2,9,9,101,5,9,9,4,9,99,3,9,1002,9,2,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,101,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,99,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,1001,9,2,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,1,9,4,9,99,3,9,1002,9,2,9,4,9,3,9,1002,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,1,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,102,2,9,9,4,9,99,3,9,102,2,9,9,4,9,3,9,101,1,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1002,9,2,9,4,9,3,9,102,2,9,9,4,9,3,9,1002,9,2,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,2,9,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,1,9,9,4,9,99,3,9,101,1,9,9,4,9,3,9,101,1,9,9,4,9,3,9,101,1,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,3,9,101,2,9,9,4,9,3,9,102,2,9,9,4,9,3,9,1001,9,1,9,4,9,3,9,1001,9,2,9,4,9,99];
+
+    let mut max_storage = 0;
+    let mut max_settings: Vec<i32> = Vec::new();
+
+    {
+        let settings = vec![0, 1, 2, 3, 4];
+        // Cheese.
+        for permutation in settings.into_iter().permutations(5) {
+            //println!("{:?}", permutation);
+            let storage = run_amplifiers(&program, permutation.clone());
+            if storage > max_storage {
+                max_storage = storage;
+                max_settings = permutation.clone();
+            }
+        }
+        println!("[Part 1] Settings {:?} produced a value of {}", max_settings, max_storage);
+    }
+
+    {
+        let settings = vec![5, 6, 7, 8, 9];
+        for permutation in settings.into_iter().permutations(5) {
+            let storage = run_feedback_amplifiers(&program, permutation.clone());
+            if storage > max_storage {
+                max_storage = storage;
+                max_settings = permutation.clone();
+            }
+        }
+        println!("[Part 2] Settings {:?} produced a value of {}", max_settings, max_storage);
+    }
+}
+
+fn run_amplifiers(program: &Vec<i32>, settings: Vec<i32>) -> i32 {
+    let mut storage: i32 = 0;
+    for setting in settings {
+        let mut input = VecDeque::from([setting, storage]);
+        let mut output: Vec<i32> = Vec::new();
+        icc::simulate(&mut program.clone(), &mut input, &mut output, 0);
+        storage = output[0];
+    }
+    return storage;
+}
+
+fn run_feedback_amplifiers(program: &Vec<i32>, settings: Vec<i32>) -> i32 {
+    let amplifiers = [
+        // program, input signal, entrypoint, setting
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+        (&mut program.clone(), &mut 0, &mut 0usize, &mut icc::Status::Running),
+    ];
+    let mut iter: i32 = 0;
+    loop {
+        for (index, setting) in settings.iter().enumerate() {
+            match amplifiers[index].3 {
+                icc::Status::Finished => {
+                    if index == 4 {
+                        // the output of amplifier 4 is stored on the input of amplifier 0
+                        return *amplifiers[0].1;
+                    }
+                    continue;
+                },
+                _ => {}
+            }
+            println!("[Iter {}] Running amplifier {} from instruction {}", iter, index, *amplifiers[index].2);
+            let mut input = if iter == 0 {
+                VecDeque::from([*setting, *amplifiers[index].1])
+            } else {
+                VecDeque::from([*amplifiers[index].1])
+            };
+            let mut output: Vec<i32> = Vec::new();
+            let result = icc::simulate(amplifiers[index].0, &mut input, &mut output, *amplifiers[index].2);
+            match result.status {
+                icc::Status::WaitingForInput => {
+                    println!("[Iter {}] Amplifier {} is waiting for input", iter, index);
+                },
+                _ => {},
+            }
+            let amp_index = (index+1) % settings.len();
+            *amplifiers[amp_index].1 = output[0];
+            println!("[Iter {}] Amplifier {}->{}: {}", iter, index, amp_index, output[0]);
+            *amplifiers[index].2 = result.instruction;
+            *amplifiers[index].3 = result.status;
+        }
+        iter += 1;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_1() {
+        let program = vec![3,15,3,16,1002,16,10,16,1,16,15,15,4,15,99,0,0];
+        let settings = vec![4, 3, 2, 1, 0];
+        assert_eq!(run_amplifiers(&program, settings), 43210);
+    }
+
+    #[test]
+    fn example_2() {
+        let program = vec![3,23,3,24,1002,24,10,24,1002,23,-1,23,101,5,23,23,1,24,23,23,4,23,99,0,0];
+        let settings = vec![0,1,2,3,4];
+        assert_eq!(run_amplifiers(&program, settings), 54321);
+    }
+
+    #[test]
+    fn example_3() {
+        let program = vec![3,31,3,32,1002,32,10,32,1001,31,-2,31,1007,31,0,33,1002,33,7,33,1,33,31,31,1,32,31,31,4,31,99,0,0,0];
+        let settings = vec![1,0,4,3,2];
+        assert_eq!(run_amplifiers(&program, settings), 65210);
+    }
+
+    #[test]
+    fn part2_example_1() {
+        let program = vec![3,26,1001,26,-4,26,3,27,1002,27,2,27,1,27,26,27,4,27,1001,28,-1,28,1005,28,6,99,0,0,5];
+        let settings = vec![9,8,7,6,5];
+        assert_eq!(run_feedback_amplifiers(&program, settings), 139629729);
+    }
+
+    #[test]
+    fn part2_example_2() {
+        let program = vec![3,52,1001,52,-5,52,3,53,1,52,56,54,1007,54,5,55,1005,55,26,1001,54,-5,54,1105,1,12,1,53,54,53,1008,54,0,55,1001,55,1,55,2,53,55,53,4,53,1001,56,-1,56,1005,56,6,99,0,0,0,0,10];
+        let settings = vec![9,7,8,5,6];
+        assert_eq!(run_feedback_amplifiers(&program, settings), 18216);
+    }
+}

icc/Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "icc"
-version = "0.1.0"
+version = "1.0.0"

icc/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "icc"
-version = "0.1.0"
+version = "1.0.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

icc/src/lib.rs

@@ -1,5 +1,20 @@
-pub fn simulate(v: &mut Vec<i32>, input: i32, output: &mut i32) -> Option<i32> {
-    let mut pos = 0;
+use std::collections::VecDeque;
+
+#[derive(Debug)]
+#[derive(PartialEq)]
+pub enum Status {
+    Running,
+    Finished,
+    WaitingForInput,
+}
+
+pub struct Result {
+    pub status: Status,
+    pub instruction: usize,
+}
+
+pub fn simulate(v: &mut Vec<i32>, input: &mut VecDeque<i32>, output: &mut Vec<i32>, start: usize) -> Result {
+    let mut pos = start;
     loop {
         let mut code = v[pos];
         // Opcodes are ABCDE, where the op is DE
@@ -57,7 +72,15 @@ pub fn simulate(v: &mut Vec<i32>, input: i32, output: &mut i32) -> Option<i32> {
         else if op == 3 {
             // Input
             let dest = v[pos+1] as usize;
-            v[dest] = input;
+            v[dest] = if input.len() == 0 {
+                return Result {
+                    status: Status::WaitingForInput,
+                    instruction: pos
+                };
+            } else {
+                input.pop_front().expect("Input stack empty... weird")
+            };
+            println!("Input: {}", v[dest]);
             pos += 2;
         }
         else if op == 4 {
@@ -68,8 +91,8 @@ pub fn simulate(v: &mut Vec<i32>, input: i32, output: &mut i32) -> Option<i32> {
             else {
                 v[v[pos+1] as usize]
             };
-            println!("{}", d);
-            *output = d;
+            println!("Output: {}", d);
+            output.push(d);
             pos += 2;
         }
         else if op == 5 {
@@ -155,7 +178,10 @@ pub fn simulate(v: &mut Vec<i32>, input: i32, output: &mut i32) -> Option<i32> {
             panic!("Unknown opcode: {}", code);
         }
     }
-    return None;
+    return Result {
+        status: Status::Finished,
+        instruction: 0
+    };
 }
 
 #[cfg(test)]
@@ -164,32 +190,36 @@ mod tests {
     #[test]
     fn test_op_1() {
         let mut program = vec![1, 0, 0, 0, 99];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[0], 2);
     }
 
     #[test]
     fn test_op_2() {
         let mut program = vec![2, 3, 0, 3, 99];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[3], 6);
     }
 
     #[test]
     fn test_case_3() {
         let mut program = vec![2,4,4,5,99,0];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[program.len() - 1], 9801);
     }
 
     #[test]
     fn test_case_4() {
         let mut program = vec![1,1,1,4,99,5,6,0,99];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[0], 30);
         assert_eq!(program[4], 2);
     }
@@ -197,103 +227,122 @@ mod tests {
     #[test]
     fn immediate_mode_multiply() {
         let mut program = vec![1002,4,3,4,33];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[4], 99);
     }
 
     #[test]
     fn negative_integers() {
         let mut program = vec![1101,100,-1,4,0];
-        let mut output: i32 = 0;
-        simulate(&mut program, 0, &mut output);
+        let mut input: VecDeque<i32> = VecDeque::new();
+        let mut output: Vec<i32> = Vec::new();
+        simulate(&mut program, &mut input, &mut output, 0);
         assert_eq!(program[4], 99);
     }
 
     #[test]
     fn position_mode_input_equal_to_8() {
         let mut program = vec![3,9,8,9,10,9,4,9,99,-1,8];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 1);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 7, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([7]), &mut output, 0);
+        assert_eq!(output[0], 0);
     }
 
     #[test]
     fn position_mode_input_less_than_8() {
         let mut program = vec![3,9,7,9,10,9,4,9,99,-1,8];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 0);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 7, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([7]), &mut output, 0);
+        assert_eq!(output[0], 1);
     }
 
     #[test]
     fn immediate_mode_input_equal_to_8() {
         let mut program = vec![3,3,1108,-1,8,3,4,3,99];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 1);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 7, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([7]), &mut output, 0);
+        assert_eq!(output[0], 0);
     }
 
     #[test]
     fn immediate_mode_input_less_than_8() {
         let mut program = vec![3,3,1107,-1,8,3,4,3,99];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 0);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 7, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([7]), &mut output, 0);
+        assert_eq!(output[0], 1);
     }
 
     #[test]
     fn position_mode_input_is_non_zero() {
         let mut program = vec![3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 1);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 0, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([0]), &mut output, 0);
+        assert_eq!(output[0], 0);
     }
 
     #[test]
     fn immediate_mode_input_is_non_zero() {
         let mut program = vec![3,3,1105,-1,9,1101,0,0,12,4,12,99,1];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 1);
+        simulate(&mut program, &mut VecDeque::from([9]), &mut output, 0);
+        assert_eq!(output[0], 1);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 0, &mut output);
-        assert_eq!(output, 0);
+        simulate(&mut program, &mut VecDeque::from([0]), &mut output, 0);
+        assert_eq!(output[0], 0);
     }
 
     #[test]
     fn multi_jump() {
         let mut program = vec![3,21,1008,21,8,20,1005,20,22,107,8,21,20,1006,20,31,1106,0,36,98,0,0,1002,21,125,20,4,20,1105,1,46,104,999,1105,1,46,1101,1000,1,20,4,20,1105,1,46,98,99];
-        let mut output: i32 = 0;
+        let mut output: Vec<i32> = Vec::new();
         let backup = program.clone();
-        simulate(&mut program, 7, &mut output);
-        assert_eq!(output, 999);
+        simulate(&mut program, &mut VecDeque::from([7]), &mut output, 0);
+        assert_eq!(output[0], 999);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 8, &mut output);
-        assert_eq!(output, 1000);
+        simulate(&mut program, &mut VecDeque::from([8]), &mut output, 0);
+        assert_eq!(output[0], 1000);
+        output.clear();
         program = backup.clone();
-        simulate(&mut program, 9, &mut output);
-        assert_eq!(output, 1001);
+        simulate(&mut program, &mut VecDeque::from([9]), &mut output, 0);
+        assert_eq!(output[0], 1001);
+    }
+
+    #[test]
+    fn blocks_on_input() {
+        let mut program = vec![3,26,1001,26,-4,26,3,27,1002,27,2,27,1,27,26,27,4,27,1001,28,-1,28,1005,28,6,99,0,0,5];
+        let mut output: Vec<i32> = Vec::new();
+        let result = simulate(&mut program, &mut VecDeque::from([9, 0]), &mut output, 0);
+        assert_eq!(result.status, Status::WaitingForInput);
+        assert_eq!(result.instruction, 6);
     }
 }