【LeetCode】Unique Paths

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?

Above is a 3 x 7 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

思路：从底层开始往上，依次相加并存储起来然后再依次求出上一层。

class Solution {public:    int uniquePaths(int m, int n) {        if(1>m||1>n)return 0;        if(1==m||1==n)return 1;        int a[m][n];        int i=0,j=0;        for(;i<m;i++){            for(j=0;j<n;j++){                if(0==i||0==j){                    a[i][j]=1;                }else{                    a[i][j]=a[i-1][j]+a[i][j-1];                }            }        }        return a[m-1][n-1];    }};