题目描述：
    image.png
    image.png

    1. //dp
    2. class Solution {
    3.     public int climbStairs(int n) {
    4.         if (n == 1) {
    5.             return 1;
    6.         }
    7.         int[] dp = new int[n];
    8.         dp[0] = 1;
    9.         dp[1] = 2;
    10.         for (int i = 2; i < n; i++) {
    11.             dp[i] = dp[i - 1] + dp[i - 2];
    12.         }
    13.         return dp[n - 1];
    14.     }
    15. }