problems(rs): add “1091. Shortest Path in Binary Matrix”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/shortest-path-in-binary-matrix.rs

@@ -0,0 +1,106 @@
+use std::collections::VecDeque;
+use std::convert::TryInto;
+
+struct Solution {}
+impl Solution {
+    pub fn shortest_path_binary_matrix(grid: Vec<Vec<i32>>) -> i32 {
+        let n = grid.len();
+
+        // create an array of distances
+        let mut distances = grid.clone();
+        for y in 0..n {
+            for x in 0..n {
+                distances[y][x] = -1;
+            }
+        }
+
+        // initialize the start with an initial distance
+        let mut q: VecDeque<(usize, usize)> = VecDeque::new();
+        if grid[0][0] == 0 {
+            distances[0][0] = 1;
+            q.push_back((0, 0));
+        }
+
+        while let Some((y, x)) = q.pop_front() {
+            if (y, x) == (n - 1, n - 1) {
+                break;
+            }
+
+            for (next_y, next_x) in (-1_isize..=1)
+                .flat_map(|dy| (-1_isize..=1).map(move |dx| (dy, dx)))
+                .map(|(dy, dx)| (y as isize + dy, x as isize + dx))
+                .filter(|&(next_y, next_x)| {
+                    (next_y, next_x) != (y as isize, x as isize)
+                        && next_y >= 0
+                        && next_y < n.try_into().unwrap()
+                        && next_x >= 0
+                        && next_x < n.try_into().unwrap()
+                })
+            {
+                let (next_y, next_x) = (next_y as usize, next_x as usize);
+
+                if distances[next_y][next_x] == -1 && grid[next_y][next_x] == 0 {
+                    distances[next_y][next_x] = distances[y][x] + 1;
+                    q.push_back((
+                        (next_y as isize).try_into().unwrap(),
+                        (next_x as isize).try_into().unwrap(),
+                    ));
+                }
+            }
+        }
+
+        distances[n - 1][n - 1]
+    }
+}
+
+fn main() {
+    assert_eq!(
+        Solution::shortest_path_binary_matrix(vec![vec![0, 1], vec![1, 0]]),
+        2
+    );
+    assert_eq!(
+        Solution::shortest_path_binary_matrix(vec![vec![0, 0, 0], vec![1, 1, 0], vec![1, 1, 0]]),
+        4
+    );
+    assert_eq!(
+        Solution::shortest_path_binary_matrix(vec![vec![1, 0, 0], vec![1, 1, 0], vec![1, 1, 0]]),
+        -1
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_1() {
+        assert_eq!(
+            Solution::shortest_path_binary_matrix(vec![vec![0, 1], vec![1, 0]]),
+            2
+        );
+    }
+
+    #[test]
+    fn example_2() {
+        assert_eq!(
+            Solution::shortest_path_binary_matrix(vec![
+                vec![0, 0, 0],
+                vec![1, 1, 0],
+                vec![1, 1, 0]
+            ]),
+            4
+        );
+    }
+
+    #[test]
+    fn example_3() {
+        assert_eq!(
+            Solution::shortest_path_binary_matrix(vec![
+                vec![1, 0, 0],
+                vec![1, 1, 0],
+                vec![1, 1, 0]
+            ]),
+            -1
+        );
+    }
+}