题目

法1：二维DP

必须掌握！

class Solution {public int uniquePaths(int m, int n) {int[][] matrix = new int[m][n];Arrays.fill(matrix[0], 1);for (int i = 0; i < m; ++i) {matrix[i][0] = 1;}for (int i = 1; i < m; ++i) {for (int j = 1; j < n; ++j) {matrix[i][j] = matrix[i - 1][j] + matrix[i][j - 1];}}return matrix[m - 1][n - 1];}
}