19.2.12 [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?

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

 1 class Solution {
 2 public:
 3     int climbStairs(int n) {
 4         vector<int>dp(n + 1,0);
 5         dp[n] = 1;
 6         for (int i = n; i >= 0; i--) {
 7             if (i + 1 <= n)dp[i] += dp[i + 1];
 8             if (i + 2 <= n)dp[i] += dp[i + 2];
 9         }
10         return dp[0];
11     }
12 };

是用n步到达目的地而不是路有n单位长度