leetcode:Climbing Stairs

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