Solution to the third task

solution.go

import (
	"sort"
)

func Solution(A []int, D int) int {
	invertTimeWithStone := invertTimeWithStone(A)

	for i := 0; i <= len(invertTimeWithStone); i++ {
		var currentRevealedStones []int = make([]int, i)
		copy(currentRevealedStones, invertTimeWithStone[:i])
		maxDistance := maxDistanceJumped(currentRevealedStones, D)

		if maxDistance + D >= len(A) {
			return i;
		}
	}

	return -1;
}

func invertTimeWithStone(A []int) []int{
	timeStoneAppears := make([]int, len(A) + 1)
	for i := 0; i < len(A); i++ {
		if A[i] >= 0 {
			timeStoneAppears[A[i]] = i
		}
	}

	return timeStoneAppears
}

func maxDistanceJumped(A []int, maxJump int) int {
	sort.Ints(A)
	currentPosition := -1
	var oldPosition int

	for {
		oldPosition = currentPosition
		for time := len(A) - 1; time >=0 ; time-- {
			if currentPosition + maxJump >= A[time] {
				currentPosition = A[time]
				break
			}
		}
		if currentPosition == oldPosition {
			break
		}
	}

	return currentPosition
}