Min Cost Climbing Stairs

Posted 2020-10-27 jiadyang

On a staircase, the i-th step has some non-negative cost cost[i] assigned (0 indexed).

Once you pay the cost, you can either climb one or two steps. You need to find minimum cost to reach the top of the floor, and you can either start from the step with index 0, or the step with index 1.

Example 1:

Input: cost = [10, 15, 20]
Output: 15
Explanation: Cheapest is start on cost[1], pay that cost and go to the top.

 

Example 2:

Input: cost = [1, 100, 1, 1, 1, 100, 1, 1, 100, 1]
Output: 6
Explanation: Cheapest is start on cost[0], and only step on 1s, skipping cost[3].

 

Note:

1. cost will have a length in the range [2, 1000].
2. Every cost[i] will be an integer in the range [0, 999].

这题是相对比较简单的动态规划的题目了，可以得到这么个式子，dp[i] = min(dp[i-1], dp[i-2]) + cost[i], 这题比较要注意的就是最后出要加个0：

 1 class Solution {
 2 public:
 3     int minCostClimbingStairs(vector<int>& cost) {
 4  
 5         cost.push_back(0);//!!
 6         int n = cost.size();
 7         
 8         vector<int> res(n, 0);
 9         res[0] = cost[0];
10         res[1] = cost[1];
11         
12         for(int i = 2; i < n; ++i)
13         {
14             res[i]=min(res[i-1], res[i-2])+cost[i];
15         }
16         
17         return res[n-1];
18     }
19 };