【leetcode】unique paths

问题:

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.

分析:

1、采用DFS,时间复杂度O(n^4),大集合会超时;采用DFS+缓冲(即“备忘录”法)时间O(n^2)。

2、用动规,时间O(n^2),空间O(n^2);可以优化,后续补上。

3、还可以用数学公式,后续补上。

代码:

class Solution {
public:
    int uniquePaths(int m, int n) {
        vector> p(m,vector(n,1));
        //边界
        for(int i=0;i


你可能感兴趣的:(面试题,leetcode)