question130.js

/**
 * @name Surrounded Regions
 * @param {character[][]} board
 * @return {void} Do not return anything, modify board in-place instead.
 */
const solve = function (board) {
    let m = board.length;
    if (m == 0) {
        return;
    }
    let n = board[0].length;
    let cannot = {};
    let dfs = (i, j) => {
        // 越界、标示过或者非相连O下return
        if (
            i < 0 ||
            j < 0 ||
            i == m ||
            j == n ||
            board[i][j] != 'O' ||
            cannot[i + '-' + j]
        ) {
            return;
        }
        cannot[i + '-' + j] = true;
        dfs(i - 1, j);
        dfs(i + 1, j);
        dfs(i, j - 1);
        dfs(i, j + 1);
    };
    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            // 从边缘O出发寻找其相连点都标示为不可替换
            if (
                (i == 0 || j == 0 || i == m - 1 || j == n - 1) &&
                board[i][j] == 'O'
            ) {
                dfs(i, j);
            }
        }
    }
    // 规避边界条件去循环
    for (let i = 1; i < m - 1; i++) {
        for (let j = 1; j < n - 1; j++) {
            if (!cannot[i + '-' + j] && board[i][j] == 'O') {
                board[i][j] = 'X';
            }
        }
    }
};
solve([]);