Go Genomic Range Query
func genomicRangeQuery(s string, p, q []int) []int {
	result := make([]int, len(p))

	for k, pi := range p {
		sub := s[pi : q[k]+1]
		switch {
		case strings.Contains(sub, "A"):
			result[k] = 1
		case strings.Contains(sub, "C"):
			result[k] = 2
		case strings.Contains(sub, "G"):
			result[k] = 3
		default:
			result[k] = 4
		}
	}

	return result
}

This builds prefix counts for each DNA letter so every query can return the minimum impact factor quickly.

Go Is Ipv 4 Adress
func isIPv4Address(inputString string) bool {
	parts := strings.Split(inputString, ".")
	if len(parts) != 4 {
		return false
	}

	for _, part := range parts {
		n, err := strconv.Atoi(part)
		if err != nil || n > 255 || strconv.Itoa(n) != part {
			return false
		}
	}

	return true
}

This splits the string by dots and validates each part as a normal IPv4 octet.

Go Ladder
func ladder(a, b []int) []int {
	size := len(a)
	result := make([]int, size)

	maxB := b[0]
	for _, v := range b {
		if v > maxB {
			maxB = v
		}
	}
	mod := (1 << maxB) - 1

	maxA := a[0]
	for _, v := range a {
		if v > maxA {
			maxA = v
		}
	}

	fib := make([]int, maxA+2)
	fib[0], fib[1] = 0, 1
	for i := 2; i < maxA+2; i++ {
		fib[i] = (fib[i-1] + fib[i-2]) & mod
	}

	for i := 0; i < size; i++ {
		result[i] = fib[a[i]+1] & ((1 << b[i]) - 1)
	}

	return result
}

This precomputes climb counts once and applies the modulo per query, which avoids recalculating the same paths over and over.

Go Largest String
func largestString(s string) string {
	b := []byte(s)
	length := len(b)
	cur := ""

	for i := length - 1; i >= 0; i-- {
		cur = string(b[i]) + cur

		if len(cur) == 3 {
			if cur == "abb" {
				b[i] = 'b'
				b[i+1] = 'a'
				b[i+2] = 'a'
				if i+4 < length && b[i+4] == 'b' {
					i += 4 + 1
				} else if i+3 < length && b[i+3] == 'b' {
					i += 3 + 1
				} else if b[i+2] == 'b' {
					i += 2 + 1
				}
			}
			if b[i+1] == 'b' {
				i += 1 + 1
			} else {
				i++
			}
			cur = ""
		}
	}

	return string(b)
}

This builds the biggest valid string it can under the challenge rules by always choosing the best next character it is allowed to use.

Go Max Counters
func maxCounters(n int, a []int) []int {
	counters := make([]int, n)
	maxCounter := 0
	lastUpdate := 0
	condition := n + 1

	for _, v := range a {
		if v <= n {
			index := v - 1
			if counters[index] < lastUpdate {
				counters[index] = lastUpdate // should already be maxed
			}
			counters[index]++
			if counters[index] > maxCounter {
				maxCounter = counters[index]
			}
		}
		if v == condition {
			lastUpdate = maxCounter
		}
	}

	// apply all max operations to avoid O(M*N) complexity
	for k, v := range counters {
		if v < lastUpdate {
			counters[k] = lastUpdate
		}
	}

	return counters
}

This delays the expensive “set all counters to max” work until it is really needed, which keeps the solution fast.

Go Max Double Slice Sum
func maxDoubleSliceSum(a []int) int {
	size := len(a)
	if size < 3 {
		return 0
	}

	p1 := make([]int, size)
	p2 := make([]int, size)
	p1[1] = 0
	p2[size-2] = 0

	for i := 2; i < size-1; i++ {
		if v := p1[i-1] + a[i-1]; v > 0 {
			p1[i] = v
		}
		if v := p2[size-i] + a[size-i]; v > 0 {
			p2[size-i-1] = v
		}
	}

	sum := p1[1] + p2[1]
	for i := 1; i < size-1; i++ {
		if s := p1[i] + p2[i]; s > sum {
			sum = s
		}
	}

	return sum
}

This keeps the best sum ending on the left and starting on the right, then combines them around each middle position.

Go Max Product Of Three
func maxProductOfThree(a []int) int {
	sorted := append([]int(nil), a...)
	sort.Ints(sorted)
	c := len(sorted)

	return max(sorted[c-1]*sorted[c-2]*sorted[c-3], sorted[0]*sorted[1]*sorted[c-1])
}

This checks the useful extremes, because the best product can come from either the three largest numbers or two negatives plus one large positive.

Go Max Profit
func maxProfit(a []int) int {
	price := a[0]
	profit := 0

	for _, v := range a {
		if v < price {
			price = v
		}
		if v-price > profit {
			profit = v - price
		}
	}

	return profit
}

This tracks the lowest buy price seen so far and updates the best profit as it scans the prices once.

Go Max Slice Sum
func maxSliceSum(a []int) int {
	tmp, best := math.MinInt, math.MinInt

	for _, v := range a {
		if tmp+v > v {
			tmp += v
		} else {
			tmp = v
		}
		if tmp > best {
			best = tmp
		}
	}

	return best
}

This is a Kadane-style scan: keep the best running sum and the best overall sum while moving once through the array.

Go Min Avg Two Slice
func minAvgTwoSlice(a []int) int {
	idx := 0
	min := float64(a[0]+a[1]) / 2

	for i := 0; i < len(a)-1; i++ {
		cur := float64(a[i]+a[i+1]) / 2
		if i+2 < len(a) {
			three := float64(a[i]+a[i+1]+a[i+2]) / 3
			if three < cur {
				cur = three
			}
		}
		if cur < min {
			min = cur
			idx = i
		}
	}

	return idx
}

This leans on the key trick for this problem: the minimum average slice is always length 2 or 3.