Day 08 part1

diff --git a/Cargo.toml b/Cargo.toml
index c7438f7..7db3d01 100644 (file)
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,4 +7,5 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-itertools = "0.8"
\ No newline at end of file
+itertools = "0.8"
+image = "0.22"
\ No newline at end of file

diff --git a/src/day07.rs b/src/day07.rs
index 77d8c48..e69de29 100644 (file)
--- a/src/day07.rs
+++ b/src/day07.rs
@@ -1 +0,0 @@
-fn fun() { }
\ No newline at end of file

diff --git a/src/day08.rs b/src/day08.rs
index e69de29..074a632 100644 (file)
--- a/src/day08.rs
+++ b/src/day08.rs
@@ -0,0 +1,52 @@
+pub fn read_from_string(raw: &str) -> Vec<u8> {
+    raw.chars().map(|c| c.to_digit(10).unwrap() as u8).collect::<Vec<u8>>()
+}
+
+pub fn decode_image(digits: &[u8], width: usize, height: usize) -> Vec<Vec<u8>> {
+    let nb_pixel = width * height;
+    let nb_layers = digits.len() / nb_pixel;
+    let mut layers: Vec<Vec<u8>> = Vec::new();
+    for i in 0 .. nb_layers {
+        let layer: Vec<u8> = Vec::from(&digits[i * nb_pixel .. (i+1) * nb_pixel]);
+        layers.push(layer);
+    }
+    layers
+}
+
+pub fn layer_with_fewer_0(layers: &[Vec<u8>]) -> &Vec<u8> {
+    let mut min = std::u32::MAX;
+    let mut layer_min = 0;
+    for i in 0 .. layers.len() {
+        let sum = layers[i].iter().fold(0, |sum, pix| if *pix == 0u8 { sum + 1 } else { sum });
+        if sum < min {
+            min = sum;
+            layer_min = i;
+        }
+    }
+    &layers[layer_min]
+}
+
+pub fn one_digits_times_two_digits(layer: &[u8]) -> i32 {
+    let (nb_1, nb_2) =
+        layer
+            .iter()
+            .fold(
+                (0, 0),
+                |(nb_1, nb_2), pix|
+                    match *pix { 1u8 => (nb_1 + 1, nb_2), 2u8 => (nb_1, nb_2 + 1), _ => (nb_1, nb_2)}
+            );
+    nb_1 * nb_2
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1() {
+        let raw = read_from_string("123456789012");
+        let layers = decode_image(&raw, 3, 2);
+        let layer = layer_with_fewer_0(&layers[..]);
+        assert_eq!(one_digits_times_two_digits(layer), 1);
+    }
+}
\ No newline at end of file

diff --git a/src/main.rs b/src/main.rs
index 2c96367..470327b 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -53,11 +53,16 @@ fn day07() -> String {
 }
 
 fn day08() -> String {
-    format!("")
+    let img = fs::read_to_string("data/day08.input").unwrap();
+
+    let raw = day08::read_from_string(&img);
+    let layers = day08::decode_image(&raw, 25, 6);
+    let layer = day08::layer_with_fewer_0(&layers[..]);
+    format!("part1: {}, part2: {}", day08::one_digits_times_two_digits(layer), 1)
 }
 
 fn day09() -> String {
-    let code = common::read_list_of_numbers("data/day09.input", ",");
+    let code = common::read_list_of_numbers::<&str, i64>("data/day09.input", ",");
     format!("part1: {:?}, part2: {:?}", day09::execute_op_code(&code, &[1]), day09::execute_op_code(&code, &[2]))
 }