LeetCode 70. Climbing Stairs

题目描述:

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?

斐波那契数列, 到达第n层的路径数量等于到达第n - 1层的路径数量加到达第n - 2层的路径数量.

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