Solve 06

src/lib.rs

@@ -127,3 +127,30 @@ pub const DIRECTIONS8: [IVec2; 8] = [
     IVec2::new(0, -1),
     IVec2::new(1, -1),
 ];
+
+/// Transposes a Vec of Vecs.
+///
+/// ```rust
+/// # use aoc::transpose;
+/// let input = vec![vec![1, 2, 3], vec![4, 5, 6]];
+/// let expected = vec![vec![1, 4], vec![2, 5], vec![3, 6]];
+/// assert_eq!(transpose(input), expected);
+/// ```
+///
+/// https://stackoverflow.com/a/64499219
+pub fn transpose<T>(v: Vec<Vec<T>>) -> Vec<Vec<T>> {
+    if v.is_empty() {
+        return v;
+    }
+
+    let len = v[0].len();
+    let mut iters: Vec<_> = v.into_iter().map(|n| n.into_iter()).collect();
+    (0..len)
+        .map(|_| {
+            iters
+                .iter_mut()
+                .map(|n| n.next().unwrap())
+                .collect::<Vec<T>>()
+        })
+        .collect()
+}