LeetCode 70. 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?

Note: Given n will be a positive integer.
解法1：记忆化数组

class Solution {
public:
    int value[1000]={};
    int climbStairs(int n) {
        if(n==1)return 1;
        else if(n==2)return 2;
        else{
            if(value[n-1]!=0){
                int k=value[n-1];
                int s=k+climbStairs(n-2);
                value[n]=s;
                return s;
            }
            else{
                int s=climbStairs(n-1)+climbStairs(n-2);
                value[n]=s;
                 return s;
            }

    }
}
};