A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).How many possible unique paths are there?

推荐方法：DP矩阵做法其实还可以节省一维：2D矩阵变成一维数组DP：

1 public int uniquePaths(int m, int n) { 2     if(m<=0 || n<=0) 3         return 0; 4     int[] res = new int[n]; 5     res[0] = 1; 6     for(int i=0;i

一维DP方法2：

1 public class Solution { 2     public int uniquePaths(int m, int n) { 3         if (m == 0 || n == 0) return 0; 4         int[] res = new int[n]; 5         for (int k=0; k