LeetCode:Climbing Stairs

Climbing Stairs

Total Accepted: 107240  Total Submissions: 291664  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?

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  Dynamic Programming

c++ code:

class Solution {
public:
    int climbStairs(int n) {
        if(1==n) return 1;
        if(2==n) return 2;
        int a=1,b=2;
        for(int i=3;i<=n;i++) {
            b = a + b;
            a = b - a;
        }
        return b;
    }
};