LeetCode 1020. Number of Enclaves

Problem Statement

Typical DFS. Similar to 1254. Number of Closed Islands

impl Solution {

    fn dfs(a : &mut Vec<Vec<i32>>, x : usize, y : usize) -> () {
        let (m, n) = (a.len(), a[0].len());
        let (dx, dy) : ([i32; 4], [i32; 4]) = ([0, 0, 1, -1], [1, -1, 0, 0]);
        for i in 0..4 {
            let (xx, yy) : (i32, i32) = (x as i32 + dx[i], y as i32 + dy[i]);
            if xx >= m as i32 || xx < 0 || yy >= n as i32 || yy < 0 {
                continue;
            }
            let (nx, ny) = (xx as usize, yy as usize);
            if a[nx][ny] == 0 {
                continue;
            }
            a[nx][ny] = 0;
            Self::dfs(a, nx, ny);
        }
    }

    pub fn num_enclaves(a: Vec<Vec<i32>>) -> i32 {
        let mut A = a;
        let (m, n, mut ans) = (A.len(), A[0].len(), 0);
        for i in 0..m {
            for j in 0..n {
                if i == 0 || j == 0 || i == m - 1 || j == n - 1 {
                    if A[i][j] != 0 {
                        A[i][j] = 0;
                        Self::dfs(&mut A, i, j);
                    }
                }
            }
        }

        for i in 0..m {
            for j in 0..n {
                if A[i][j] != 0 {
                    ans += 1;
                }
            }
        }

        return ans;
    }
}