Quick sort recursive

quicksort.go

package main

import (
    "fmt"
    "bufio"
    "os"
)

//see Cracking Code Interview
//practice quick sort (recursive)
//input - size n on first line and space delimited item values on second line
func main() {
    var n int
    var v int
    scanner := bufio.NewReader(os.Stdin)
    _, err := fmt.Fscanf(scanner, "%d\n", &n)
    if err != nil {
        panic(err.Error())
    }
    a := make([]int, n)
    for i :=0; i <n-1; i++ {
        _, _ = fmt.Fscanf(scanner, "%d ", &v)
        a[i] = v
    }
    _, _ = fmt.Fscanf(scanner, "%d\n", &v)
    a[n-1] = v

    quicksort(a, 0, n -1)
    fmt.Printf("%v\n", a)
}

func quicksort(a []int, left int, right int) {
	if left >= right {
		return
	}
	pivot := a[left + (right - left)/2]
	index := partition(a, left, right, pivot)
	quicksort(a, left, index-1)
	quicksort(a, index, right)
}

func partition(a []int, left int, right int, pivot int) int {
	i := left
	j := right
	//The bookend indices move toward the middle
	for ; ; {
		if i >= j {
			break
		}
		//Move left towards the right until a value is >pivot
		for ; a[i] < pivot && i <j; {
		    //Move left towards the right until a value is >pivot
		    i++
		}
		for ; a[j] > pivot && j >i; {
		    //Move right towards the left until a value is <pivot
		    j--
		}
		if i <= j {
			//Indices should be resting on values that need swap
			swap(a, i, j)
			i++
			j--
		}
	}

	return i
}

func swap(a []int, i int, j int) {
	tmp := a[i]
	a[i] = a[j]
	a[j] = tmp
}