Go算法——堆排序

package main

import (
    "fmt"
    "math"
)

func parent(i int) int {
    return i >> 1
}

func left(i int) int {
    return i << 1
}

func right(i int) int {
    return i<<1 + 1
}

func buildMaxHeap(array []int) {
    heapSize := len(array) - 1
    for i := heapSize / 2; i > 0; i-- {
        maxHeapify(array, heapSize, i)
    }
}

func maxHeapify(array []int, heapSize, i int) {
    l, r := left(i), right(i)
    largest := i
    if l <= heapSize && array[l] > array[i] {
        largest = l
    }
    if r <= heapSize && array[r] > array[largest] {
        largest = r
    }
    if largest != i {
        array[largest], array[i] = array[i], array[largest]
        maxHeapify(array, heapSize, largest)
    }
}

func printArray(array []int) {
    for i := 1; i < len(array); i = i << 1 {
        for k := 0; k < i && k+i < len(array); k++ {
            fmt.Print(array[i+k], " ")
        }
        fmt.Println()
    }
}

func heapSort(array []int) {
    buildMaxHeap(array)
    heapSize := len(array) - 1
    for i := len(array) - 1; i > 1; i-- {
        array[i], array[1] = array[1], array[i]
        heapSize--
        maxHeapify(array, heapSize, 1)
    }
}

func main() {
    arr := []int{math.MaxInt64, 13, -3, -25, 20, -3, -16, -23, 18, 20, -7, 12, -5, -22, 15, -4, 7}
    printArray(arr)
    buildMaxHeap(arr)
    printArray(arr)
    heapSort(arr)
    fmt.Println(arr)
}

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