题目

假设有一个超长的切片，切片的元素类型为int，切片中的元素为乱序排列。限时5秒，使用多个goroutine查找切片中是否存在给定值，在找到目标值或者超时后立刻结束所有goroutine的执行。

比如切片为：[23, 32, 78, 43, 76, 65, 345, 762, …… 915, 86]，查找的目标值为345，如果切片中存在目标值程序输出:"Found it!"并且立即取消仍在执行查找任务的goroutine。如果在超时时间未找到目标值程序输出:“Timeout! Not Found”，同时立即取消仍在执行查找任务的goroutine。

思路

思路参考：上周并发题的解题思路以及介绍Go语言调度器

代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
package main

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

func main() {
	targetNum := 898982
	total := 2000000000
	s := GetRandomSlice(total, 200000000, targetNum)
	t := time.Now()
	manager := NewManager(250000000)
	manager.Search(s, targetNum)
	fmt.Println(manager.Result())
	fmt.Printf("find the number of %d, time conumin %v\n", total, time.Since(t))
}

func GetRandomSlice(sliceLen int, randNum int, targetNum int) []int {
	tmp := make([]int, sliceLen)
	rand.Seed(time.Now().UnixNano())
	for i := 0; i < sliceLen; i++ {
		randNum := rand.Intn(randNum)
		tmp[i] = randNum
		if randNum == targetNum {
			fmt.Println("randNum is ", i)
		}
	}
	return tmp
}

type Manager struct {
	s         []int
	targetNum int
	chunkSize int
	chunkNum  int
	once      sync.Once
	ctx       context.Context
	cancel    func()
	result    chan string
}

func NewManager(chunkSize int) *Manager {
	ctx, cancel := context.WithCancel(context.Background())
	return &Manager{
		chunkSize: chunkSize,
		once:      sync.Once{},
		ctx:       ctx,
		cancel:    cancel,
		result:    make(chan string),
	}
}

func (m *Manager) Search(s []int, target int) {
	m.s = s
	m.targetNum = target
	Chunk(len(s), m.chunkSize, m.Worker)
}

func Chunk(total, chunkSize int, f func(part, startIndex, endIndex int)) {
	if total%chunkSize == 0 {
		for i := 0; i < total/chunkSize; i++ {
			e := (i + 1) * chunkSize
			f(i+1, i*chunkSize, e)
		}
	} else {
		for i := 0; i <= total/chunkSize; i++ {
			e := (i + 1) * chunkSize
			if i == (total / chunkSize) {
				e = i*chunkSize + total%chunkSize
			}
			f(i+1, i*chunkSize, e)
		}
	}
}

func (m *Manager) Worker(part, startIndex, endIndex int) {
	m.chunkNum++
	go func() {
		for i, v := range m.s[startIndex:endIndex] {
			if v == m.targetNum {
				m.result <- fmt.Sprintf("Found! At index %d\n", (part-1)*m.chunkSize+i)
				return
			}
			select {
			case <-m.ctx.Done():
				return
			default:
				continue
			}
		}
		m.result <- ""
		return
	}()
}

func (m *Manager) Result() string {
	var once sync.Once
	var num int
	for {
		select {
		case <-time.After(time.Second * time.Duration(10)):
			once.Do(m.cancel)
			return "Timeout! Not Found"
		case res := <-m.result:
			if res != "" {
				once.Do(m.cancel)
				return res
			}
			num++
			if num == m.chunkNum {
				once.Do(m.cancel)
				return "All Task Done,Not Found!"
			}
		}
	}
}

参考