【回溯法】八皇后问题（递归和非递归）

// test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <stdio.h>
using namespace std;

int a[9] = {0};
int n = 8;
int count = 0;

bool check(int arr[], int n)
{
    for (int i = 2; i <= n; ++i)
        for(int j = 1; j <= i-1; ++j)
            if (arr[i] == arr[j] || (abs(arr[i]-arr[j]) == abs(i-j)))
                return false;
    return true;
}

void printQueens(int a[])
{
    printf("第%d种情况：", count);
    for (int i = 1; i <= n; ++i)
        printf("%d",a[i]);
    printf("\n");
    count++;
}

void searchQueens8(int r)
{
    if (r > n)
        printQueens(a);

    for (int i = 1; i <= n; ++i)
    {
        a[r] = i;
        if (check(a, r))
        {
            searchQueens8(r+1);
        }
    }
}


int _tmain(int argc, _TCHAR* argv[])
{
    searchQueens8(1);
    return 0;
}

#pragma once
#include "stdafx.h"

const int N = 8;
int cszStack[9];
int sum = 0;
int top;

void printQueenStack()
{
    printf("No.%d:", sum);
    for (int i = 1; i <= N; ++i)
        printf("%d", cszStack[i]);
    printf("\n");
    sum++;
}

// k表示第k行
bool judge(int k)
{
    if (k == 1)
        return true;

    int i;
    for (i = 1; i < k; ++i)
    {
        if (cszStack[i] == cszStack[k])
            return false;

        if (abs(k-i) == abs(cszStack[k] - cszStack[i]))
            return false;
    }

    return true;
}

void putQueen()
{
    top = 1;
    while(top > 0)
    {
        cszStack[top]++; // 摆放一个皇后
        // 如果第top行的皇后没有摆放出第8列，那就一直找到它在top行的合法位置
        while((cszStack[top] <= N) && (!judge(top)))
            cszStack[top]++;

        if (cszStack[top] <= N)
        {
            if (top == N)
            {
                printQueenStack();
                // 输出结果
            }
            else
            {
                top++;
                cszStack[top] = 0;
            }
        }
        else
        {
            // 在第top行8列全部不能放置皇后，说明前面几行的摆放不合理，所以要退回上一行
            top--;
        }
    }

}

void initStack()
{
    for (int i = 0; i <= N; ++i )
        cszStack[i] = 0;

    sum = 0;
    top = 0;
}

void searchQueueStack()
{
    initStack();
    putQueen();
}

int _tmain(int argc, _TCHAR* argv[])
{
    //SearchQueens8(1);

    searchQueueStack();
    return 0;
}