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?

题解

class Solution {
public:
    int climbStairs(int n) {
        int a = 1, b = 1;
        while(n--){
            a = (b += a) - a;
        }
        return a;
    }
};