LeetCode之旅（31）

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?

很经典的题目，不能用递归，会超时

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