70. Climbing Stairs

简单dp

class Solution {public:    int climbStairs(int n) {        vector<int>ve;        for(int i = 0; i <= n; ++ i)        ve.push_back(0);        ve[1] = 1; ve[2] = 2;        for(int i = 3; i <= n; ++ i)        ve[i] = ve[i - 1] + ve[i - 2];        return ve[n];    }};