Go で map 内のデータを検索するサンプル

はじめに

Go で map 内のデータを検索するサンプル

サンプル

package main

import "errors"

func MapSearch(nums, length []int) ([]int, error) {
    targetMap := make(map[int]int, len(nums))
    for i, nums := range nums {
        targetMap[nums] = i
    }

    target := make([]int, len(length))
    for si, s := range length {
        if ti, ok := targetMap[s]; ok {
            target[si] = ti
        } else {
            return nil, errors.New("not found")
        }
    }
    return target, nil
}

func main() {
    nums := []int{1, 2, 3, 4, 5}
    length := []int{1, 3, 5}
    target, err := MapSearch(nums, length)
    if err != nil {
        println(err.Error())
        return
    }
    for _, t := range target {
        println(t)
    }
}

テスト

package main

import (
    "reflect"
    "testing"
)

func Test_MapSearch(t *testing.T) {
    tests := []struct {
        name     string
        nums     []int
        target   []int
        expected []int
    }{
        {"MapSearch", []int{1, 2, 3, 4, 5}, []int{1, 3, 5}, []int{0, 2, 4}},
    }

    fv := reflect.ValueOf(MapSearch)
    name := runtime.FuncForPC(fv.Pointer()).Name()

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got, err := MapSearch(tt.nums, tt.target)
            if err != nil {
                t.Errorf("Error: %v", err)
            }

            if !reflect.DeepEqual(got, tt.expected) {
                t.Errorf(name+"() = %v, want %v", got, tt.expected)
            }
        })
    }
}

ベンチマークコード

package main

import (
    "testing"
)

func makeSeqNums(count int) []int {
    nums := make([]int, count)
    for i := 0; i < count; i++ {
        nums[i] = i + 1
    }
    return nums
}

func BenchmarkMapSearch(b *testing.B) {
    nums := makeSeqNums(10000)
    target := makeSeqNums(50000)

    b.ResetTimer()

    for i := 0; i < b.N; i++ {
        MapSearch(nums, target)
    }
}

% go test -bench . -benchmem
goos: linux
goarch: amd64
pkg: go-map-search
cpu: Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz
BenchmarkMapSearch-2        1310        875660 ns/op      723626 B/op         13 allocs/op
PASS
ok      go-map-search   1.252s