LeetCode 1254. Number of Closed Islands

Problem Statement

Typical BFS.

use std::collections::VecDeque;

impl Solution {
    pub fn closed_island(grid: Vec<Vec<i32>>) -> i32 {
        let (m, n, mut ans) = (grid.len(), grid[0].len(), 0);
        let (dx, dy) : ([i32; 4], [i32; 4]) = ([1, -1, 0, 0], [0, 0, 1, -1]);
        let mut g = grid;
        for i in 0..m {
            for j in 0..n {
                if g[i][j] == 1 || g[i][j] == -1 {
                    continue;
                }
                let mut q = VecDeque::new();
                q.push_back((i, j));
                g[i][j] = -1;
                let mut valid = true;

                while !q.is_empty() {
                    let (x, y) = q.pop_front().unwrap();
                    for k in 0..4 {
                        let (xx, yy) = (x as i32 + dx[k], y as i32 + dy[k]);
                        if xx < 0 || yy < 0 || xx >= m as i32 || yy >= n as i32 {
                            valid = false; continue;
                        }
                        let (nx, ny) = (xx as usize, yy as usize);
                        if g[nx][ny] == 1 || g[nx][ny] == -1 {
                            continue;
                        }
                        q.push_back((nx, ny));
                        g[nx][ny] = -1;
                    }
                }

                if valid {
                    ans += 1;
                }
            }
        }

        return ans;
    }
}