我的js算法爬坑之旅-水位上升的泳池中游泳

第一百一十三天：力扣778题，水位上升的泳池中游泳

地址：leetcode-cn.com/problems/sw…

思路：并查集

var swimInWater = function(grid) {
    const n = grid.length;
    const f = new Array(n * n).fill(0)
                              .map((element, index) => index);

    const idx = new Array(n * n).fill(0)
                                .map(() => new Array(2).fill(0));
    for (let i = 0; i < n; i++) {
        for (let j = 0; j < n; j++) {
            idx[grid[i][j]][0] = i;
            idx[grid[i][j]][1] = j;
        }
    }

    const directions = [[0, 1], [0, -1], [1, 0], [-1, 0]];
    for (let threshold = 0; threshold < n * n; threshold++) {
        const i = idx[threshold][0], j = idx[threshold][1];
        for (const direction of directions) {
            const ni = i + direction[0], nj = j + direction[1];
            if (ni >= 0 && ni < n && nj >= 0 && nj < n && grid[ni][nj] <= threshold) {
                merge(f, i * n + j, ni * n + nj);
            }
        }
        if (find(f, 0) === find(f, n * n - 1)) {
            return threshold;
        }
    }
    return -1;
};

const find = (f, x) => {
    if (f[x] === x) {
        return x;
    }
    const fa = find(f, f[x]);
    f[x] = fa;
    return fa;
}

const merge = (f, x, y) => {
    const fx = find(f, x), fy = find(f, y);
    f[fx] = fy;
}

执行用时：144 ms, 在所有 JavaScript 提交中击败了65.22%的用户

内存消耗：43.8 MB, 在所有 JavaScript 提交中击败了60.87%的用户