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package main

import (
	"fmt"
	"math/rand"
	"time"
)

func main() {
	n := 100000000
	st := time.Now()
	test1(n)
	fmt.Println(time.Since(st))

	st = time.Now()
	test2(n)
	fmt.Println(time.Since(st))
}

func test2(n int) {
	f := 0
	r := rand.Intn(10)
	for i := 0; i < n; i++ {
		if r == 0 ||
			r == 1 ||
			r == 2 ||
			r == 3 ||
			r == 4 ||
			r == 5 ||
			r == 6 ||
			r == 7 ||
			r == 8 ||
			r == 9 {
			f += r
		}
		r = rand.Intn(10)
	}
}

func test1(n int) {
	f := 0
	r := rand.Intn(10)
	for i := 0; i < n; i++ {
		switch r {
		case 0:
			fallthrough
		case 1:
			fallthrough
		case 2:
			fallthrough
		case 3:
			fallthrough
		case 4:
			fallthrough
		case 5:
			fallthrough
		case 6:
			fallthrough
		case 7:
			fallthrough
		case 8:
			fallthrough
		case 9:
			fallthrough
		default:
			f += r
		}
		r = rand.Intn(10)
	}
}
 

4.608s

4.336s