8 Queens Problem (Backtracking)

//8 queens (backtracking)

#include <iostream>
using namespace std;


void queen_all(int k);//The algorithm function of backtracking
int col[9];
bool row[9], digLeft[17], digRight[17];


intmain()
{
	int j;


	for (j = 0; j <= 8; j++)  row[j] = true;
	for (j = 0; j <= 16; j++) digLeft[j] = digRight[j] = true;


	queen_all(1);


	return 0;
}


//Find a reasonable configuration on the Kth column of the 8*8 chessboard
void queen_all(int k)
{


	int i, j;
	char awn; //Store the flag of whether to continue searching


	for (i = 1; i <= 8;i++) //Configure the queens of K columns on rows 1 to 8 in turn


	if (row[i] && digLeft[k+i-1] && digRight[8+k-i]){                      //可行位置
		col[k] = i; //indicates row i at column K
		row[i] = digLeft[k+i-1] = digRight[8+ki] = false; // means there is a queen


		if (k == 8){ //find a feasible solution
			for (j = 1; j <= 8; j++)
				cout << j << " " << col[j] << '\t';                      //列和行


			cout << endl << "Do you need to continue searching (Q-- means exit, others continue:)";
			cin >> awn;
			if (awn == 'Q'|| awn == 'q') exit(0);
		}


		else queen_all(k + 1); // recurse to column k+1
		row[i] = digLeft[k+i-1] = digRight[8+ki] = true; // prepare for the next feasible solution


	}

}