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1 // Copyright 2011 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 package sort_test
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6
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7 import (
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8 "fmt"
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9 "sort"
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10 )
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11
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12 type Person struct {
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13 Name string
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14 Age int
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15 }
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16
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17 func (p Person) String() string {
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18 return fmt.Sprintf("%s: %d", p.Name, p.Age)
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19 }
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20
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21 // ByAge implements sort.Interface for []Person based on
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22 // the Age field.
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23 type ByAge []Person
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24
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25 func (a ByAge) Len() int { return len(a) }
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26 func (a ByAge) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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27 func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
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28
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29 func Example() {
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30 people := []Person{
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31 {"Bob", 31},
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32 {"John", 42},
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33 {"Michael", 17},
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34 {"Jenny", 26},
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35 }
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36
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37 fmt.Println(people)
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38 // There are two ways to sort a slice. First, one can define
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39 // a set of methods for the slice type, as with ByAge, and
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40 // call sort.Sort. In this first example we use that technique.
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41 sort.Sort(ByAge(people))
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42 fmt.Println(people)
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43
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44 // The other way is to use sort.Slice with a custom Less
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45 // function, which can be provided as a closure. In this
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46 // case no methods are needed. (And if they exist, they
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47 // are ignored.) Here we re-sort in reverse order: compare
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48 // the closure with ByAge.Less.
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49 sort.Slice(people, func(i, j int) bool {
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50 return people[i].Age > people[j].Age
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51 })
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52 fmt.Println(people)
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53
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54 // Output:
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55 // [Bob: 31 John: 42 Michael: 17 Jenny: 26]
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56 // [Michael: 17 Jenny: 26 Bob: 31 John: 42]
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57 // [John: 42 Bob: 31 Jenny: 26 Michael: 17]
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58 }
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