N queens problem implement code in golang

nqueen_recusive.go

package main

import (
	"fmt"
	"log"
	"os"
	"strconv"
)

const (
	intvalue = -1
)

var column []int
var N int = 8

func main() {
	var err error
	if len(os.Args) == 2 {
		N, err = strconv.Atoi(os.Args[1])
		if err != nil {
			log.Fatal(err)
		}
	}
	column = make([]int, N)
	for i := 0; i < N; i++ {
		column[i] = intvalue
	}
	place(0)
}

var count int = 0
var loop int = 0
func show() {
	count++
    fmt.Printf("loop: %d, Answer: %d\n", loop, count)
	for i := 0; i < N; i++ {
		for j := 0; j < N; j++ {
			if column[i] == j {
				fmt.Printf(" Q")
			} else {
				fmt.Printf(" .")
			}
		}
		fmt.Printf("\n")
	}
	fmt.Printf("\n")
}

func valid(i, j int) bool {
    //fmt.Printf("i=%d, j=%d\n", i, j)
	for k := 0; k <= i; k++ {
		v := column[k]
		if v == j || v-j == i-k || v-j == k-i {
			return false
		}
	}
	return true
}

func place(n int) {
    loop++
	if n >= N {
        /* all row detected, show result */
		show()
        fmt.Printf("\n")
        loop = 0
		return
	}

	for i := 0; i < N; i++ {
		if valid(n, i) {
            /* found, detect next row */
			column[n] = i
			place(n + 1)

            /* here, all row are detected 
               set column[n] to initial value, ready for next  detecting
             */
            column[n] = intvalue
		}

        /* not found, detect for next column */
	}

    /* return for backtrace */
}