LeetCode *** 70. Climbing Stairs

题目：

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

分析：

爬楼梯问题，一开始用了递归，于是TLE了。。于是用了一个数组来记录之前走的方法数。当前楼梯数n的走法可以由n-1和n-2时的走法一起得到。

代码：

class Solution {public:    int climbStairs(int n) {                int* stairs=new int[n+1];        stairs[1]=1;        stairs[2]=2;                for(int i=3;i<=n;++i){            stairs[i]=stairs[i-1]+stairs[i-2];        }        return stairs[n];    }};