benchmark.go

import (
	"testing"
)

const S = "abcdddeeeeaabbbcd"

func largeGroupPositions(S string) (res [][]int) {
	tmpSlice := make([]int, 2)
	var (
		tmpRune rune
		count   int
	)

	for i, r := range []rune(S) {
		if i == 0 {
			tmpSlice[0], tmpSlice[1] = i, i
			count++
			tmpRune = r
			continue
		}

		if r == tmpRune {
			tmpSlice[1] = i
			count++
			continue
		}

		if count >= 3 {
			res = append(res, tmpSlice)
			tmpSlice = []int{i, i}
			count = 1
			tmpRune = r
			continue
		}

		tmpSlice[0], tmpSlice[1] = i, i
		count = 1
		tmpRune = r
	}

	if count >= 3 {
		res = append(res, tmpSlice)
	}

	return
}

func largeGroupPositions2(S string) [][]int {
	r := [][]int{}
	n := len(S)
	if n < 3 {
		return r
	}
	for i := 0; i < n; i++ {
		tmpStart := i
		for i < n-1 && S[i] == S[i+1] {
			i++
		}
		tmpEnd := i
		if tmpEnd-tmpStart >= 2 {
			r = append(r, []int{tmpStart, tmpEnd})
		}
	}
	return r
}

func largeGroupPositions3(S string) (res [][]int) {
	// tmpSlice := make([]int, 2)

	var (
		tmpStart int
		tmpEnd   int
		tmpRune  rune
		count    int
	)

	for i, r := range []rune(S) {
		if i == 0 {
			// tmpSlice[0], tmpSlice[1] = i, i
			tmpStart, tmpEnd = i, i
			count++
			tmpRune = r
			continue
		}

		if r == tmpRune {
			// tmpSlice[1] = i
			tmpEnd = i
			count++
			continue
		}

		if count >= 3 {
			res = append(res, []int{tmpStart, tmpEnd})
			// tmpSlice = []int{i, i}
			count = 1
			tmpRune = r
			continue
		}

		// tmpSlice[0], tmpSlice[1] = i, i
		tmpStart, tmpEnd = i, i
		count = 1
		tmpRune = r
	}

	if count >= 3 {
		res = append(res, []int{tmpStart, tmpEnd})
	}

	return
}

func Benchmark1(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = largeGroupPositions(S)
	}
}

func Benchmark2(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = largeGroupPositions2(S)
	}
}

func Benchmark3(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = largeGroupPositions3(S)
	}
}