Add day 8

day8/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day8"
+version = "0.1.0"

day8/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day8"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day8/src/main.rs

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+struct Image {
+    width: usize,
+    height: usize,
+    layers: Vec<Vec<u32>>,
+}
+
+impl Image {
+    fn from_str(width: usize, height: usize, data: &str) -> Image {
+        assert_eq!(data.len() % (width * height), 0);
+        let mut image = Image {
+            width: width,
+            height: height,
+            layers: Vec::new(),
+        };
+        let mut layer: usize = 0;
+        image.layers.push(Vec::new());
+        let mut index: usize = 0;
+        for c in data.chars() {
+            if index >= (width*height) {
+                layer += 1;
+                image.layers.push(Vec::new());
+                index = 0;
+            }
+            image.layers[layer].push(c.to_digit(10).expect("Could not convert character to digit"));
+            index += 1;
+        }
+        return image;
+    }
+
+    fn layer_n_digits(&self, layer_index: usize, value: u32) -> usize {
+        let mut count: usize = 0;
+        for v in self.layers[layer_index].iter() {
+            if *v == value {
+                count += 1;
+            }
+        }
+        return count;
+    }
+
+    fn layer_merge(&self) -> Vec<u32> {
+        let mut result: Vec<u32> = Vec::new();
+        result.resize(self.width * self.height, 2);
+        for pixel_index in 0..(self.width*self.height) {
+            for layer_index in 0..self.layers.len() {
+                // 2 is transparent
+                let value = self.layers[layer_index][pixel_index];
+                if value != 2 {
+                    result[pixel_index] = value;
+                    break;
+                }
+            }
+        }
+        return result;
+    }
+}
+
+fn main() {
+    let data = std::fs::read_to_string("input")
+        .expect("Failed to read 'input'");
+    let image = Image::from_str(25, 6, &data);
+    println!("Image contains {} layers", image.layers.len());
+    let mut layer_fewest_zeroes: usize = 0;
+    let mut least_zeroes: usize = 200;
+    for index in 0..image.layers.len() {
+        let n_zeroes = image.layer_n_digits(index, 0);
+        if n_zeroes < least_zeroes {
+            layer_fewest_zeroes = index;
+            least_zeroes = n_zeroes;
+        }
+    }
+    println!("Layer {} has {} zeroes", layer_fewest_zeroes, least_zeroes);
+    println!("[Part 1] {}", image.layer_n_digits(layer_fewest_zeroes, 1) * image.layer_n_digits(layer_fewest_zeroes, 2));
+
+    let merged = image.layer_merge();
+    let mut n: u32 = 0;
+    for i in merged.iter() {
+        let c = if *i == 0 {
+            '⬛'
+        } else if *i == 1 {
+            '⬜'
+        }
+        else if *i == 2 {
+            ' '
+        }
+        else {
+            '?'
+        };
+        print!("{}", c);
+        n += 1;
+        if n % 25 == 0 {
+            print!("\n");
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+
+    #[test]
+    fn create_image() {
+        let data = "123456789012";
+        let image = Image::from_str(3, 2, data);
+        assert_eq!(image.layers.len(), 2);
+        let layer_0 = vec![1, 2, 3, 4, 5, 6];
+        let layer_1 = vec![7, 8, 9, 0, 1, 2];
+        assert_eq!(image.layers[0], layer_0);
+        assert_eq!(image.layers[1], layer_1);
+    }
+
+    #[test]
+    fn layer_merge() {
+        let data = "0222112222120000";
+        let image = Image::from_str(2, 2, data);
+        let merged = image.layer_merge();
+        assert_eq!(merged[0], 0);
+        assert_eq!(merged[1], 1);
+        assert_eq!(merged[2], 1);
+        assert_eq!(merged[3], 0);
+    }
+}