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?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output:  2
Explanation:  There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps

Example 2:

Input: 3
Output:  3
Explanation:  There are three ways to climb to the top.

1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

解题思路

动态规划，等价于斐波那契数列。

具体实现

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