猴子选大王

main.go

package main

import "fmt"

func main() {
	count := 10
	fmt.Printf("there are %d monkeys\n", count)
	index := selectKing(count)
	fmt.Println("the king is", index)
}

type monkey struct {
	id int // the orignal id
}

func selectKing(count int) (index int) {
	monkeys := []monkey{}
	for i := 1; i <= count; i++ {
		monkeys = append(monkeys, monkey{id: i})
	}

	fmt.Println("start to select")
	monkey := cutByNumber(3, monkeys)
	index = monkey.id
	return
}

// let's assume the number is 3
func cutByNumber(num int, monkeys []monkey) (m monkey) {
	number := 1
	for i := 0; len(monkeys) > 1; {
		if i == len(monkeys) {
			i = 0
		}

		if number == num {
			number = 1
			if i+1 > len(monkeys) {
				monkeys = monkeys[0:i]
			} else {
				monkeys = append(monkeys[0:i], monkeys[i+1:]...)
			}
		} else {
			number = number + 1
			i++
		}
	}
	m = monkeys[0]
	return
}

main_test.go

package main

import "testing"

func Test_selectKing(t *testing.T) {
	type args struct {
		count int
	}
	tests := []struct {
		name      string
		args      args
		wantIndex int
	}{{
		args:      args{count: 10},
		wantIndex: 4,
	}, {
		args:      args{count: 8},
		wantIndex: 7,
	}, {
		args:      args{count: 12},
		wantIndex: 10,
	}}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if gotIndex := selectKing(tt.args.count); gotIndex != tt.wantIndex {
				t.Errorf("selectKing() = %v, want %v", gotIndex, tt.wantIndex)
			}
		})
	}
}