62、https://leetcode-cn.com/problems/unique-paths/

    1. var uniquePaths = function(m, n) {
    2.     const f = new Array(m).fill(0).map(() => new Array(n).fill(0));
    3.     for (let i = 0; i < m; i++) {
    4.         f[i][0] = 1;
    5.     }
    6.     for (let j = 0; j < n; j++) {
    7.         f[0][j] = 1;
    8.     }
    9.     for (let i = 1; i < m; i++) {
    10.         for (let j = 1; j < n; j++) {
    11.             f[i][j] = f[i - 1][j] + f[i][j - 1];
    12.         }
    13.     }
    14.     return f[m - 1][n - 1];
    15. };