99클럽 코테 스터디 40일차 TIL Min Cost Climbing Stairs

# 오늘의 학습 키워드 

동적계획법

 

# 오늘의 문제 

https://leetcode.com/problems/min-cost-climbing-stairs/description/

You are given an integer array cost where cost[i] is the cost of ith step on a staircase. Once you pay the cost, you can either climb one or two steps.

You can either start from the step with index 0, or the step with index 1.

Return the minimum cost to reach the top of the floor.

 

Example 1:

Input: cost = [10,15,20]

Output: 15

Explanation: You will start at index 1.

- Pay 15 and climb two steps to reach the top.

The total cost is 15.

Example 2:

Input: cost = [1,100,1,1,1,100,1,1,100,1]

Output: 6

Explanation: You will start at index 0.

- Pay 1 and climb two steps to reach index 2.

- Pay 1 and climb two steps to reach index 4.

- Pay 1 and climb two steps to reach index 6.

- Pay 1 and climb one step to reach index 7.

- Pay 1 and climb two steps to reach index 9.

- Pay 1 and climb one step to reach the top.

The total cost is 6.

 

Constraints:

• 2 <= cost.length <= 1000
• 0 <= cost[i] <= 999

 

# 나의 풀이방식 

 

class Solution {
    public int minCostClimbingStairs(int[] cost) {

        // 세 번째 계단부터 최소비용 누적
        for (int i = 2; i < cost.length; i ++) { 
            cost[i] += Math.min(cost[i - 1], cost[i - 2]);
        };

        // 마지막 계단과 그 전 계단의 비용 중 최소비용 리턴
        return Math.min(cost[cost.length - 1], cost[cost.length - 2]);
    }
}