Back to ChallengesMin Cost Climbing StairsEasy 15 min

Min Cost Climbing Stairs

You are given an integer array cost where cost[i] is the cost of i-th step on a staircase. Once you pay the cost, you can climb one or two steps. You can start from index 0 or 1. Return the minimum cost to reach the top.

Examples

Input: cost = [10, 15, 20]

Output: 15

Start at index 1, pay 15, and climb two steps to reach the top.

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

Output: 6

Take the path: 0 -> 2 -> 4 -> 6 -> 7 -> 9 for total cost 6.

Constraints

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

Complexity Analysis

Time

O(n)

single pass over the cost array.

Space

O(1)

optimized space using two variable trackers.

Test Cases

#1 Simple 3-stair case

Input: [10, 15, 20]

Expected: 15

#2 Alternating small/large costs

Input: [1, 100, 1, 1, 1, 100, 1, 1, 100, 1]

Expected: 6

JavaScript

Output

Click "Run Code" to see output here...