LeetCode70. Climbing Stairs

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：若n=1,1种；n=2,2种；n=3,3种；n=4,5种；n=5,8种......即有n阶楼梯时，爬楼梯的方法数有(n-1阶所含方法数 + n-2阶所含方法数)。记得分配指针内存及释放内存，否则会The Time Limit.

class Solution {
public:
    int climbStairs(int n) {
        if(n<=3) return n;
        int *res = new int[n];
        res[0]=1;
        res[1]=2;
        res[2]=3;
        for(int i=3;i<n;i++){
            res[i] = res[i-1]+res[i-2];
        }
        int sum = res[n-1];
        delete res;//释放内存
        return sum;
    }
};