70. Climbing Stairs

70. Climbing Stairs

Total Accepted: 84498 Total Submissions: 237744 Difficulty: Easy

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?

 

class Solution {
public:
    int climbStairs(int n) {
        if(n<=2) return n;
        int pre1 = 2;
        int pre2 = 1;
        int res  = 0;
        for(int i=3;i<=n;++i){
            res  = pre1+pre2;
            pre2 = pre1;
            pre1 = res;
        }
        return res;
    }
};

Next challenges: (H) Edit Distance (H) Palindrome Partitioning II (H) Paint House II