0746.go

// Source: https://leetcode.com/problems/min-cost-climbing-stairs
// Title: Min Cost Climbing Stairs
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

// Let M(i) be cost to step i
// M(i) = min(M(i-1), M(i-2)) + cost[i]
func minCostClimbingStairs(cost []int) int {
	for i := 2; i < len(cost); i++ {
		cost[i] += _min(cost[i-1], cost[i-2])
	}
	return _min(cost[len(cost)-1], cost[len(cost)-2])
}

func _min(a, b int) int {
	if a < b {
		return a
	}
	return b
}