LeetCode – Refresh – Climbing Stairs

This is pretty simple.

Just use three element to pretain the result;

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