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nQueen.c
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nQueen.c
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#include <stdio.h>
#include <time.h>
int N;
int board[100][100];
int is_attack(int i, int j)
{
int k, l;
for (k = 0; k < N; k++)
{
if ((board[i][k] == 1) || (board[k][j] == 1))
return 1;
}
for (k = 0; k < N; k++)
{
for (l = 0; l < N; l++)
{
if (((k + l) == (i + j)) || ((k - l) == (i - j)))
{
if (board[k][l] == 1)
return 1;
}
}
}
return 0;
}
int N_queen(int n)
{
int i, j;
if (n == 0)
return 1;
for (i = 0; i < N; i++)
{
for (j = 0; j < N; j++)
{
if ((!is_attack(i, j)) && (board[i][j] != 1))
{
board[i][j] = 1;
if (N_queen(n - 1) == 1)
{
return 1;
}
board[i][j] = 0;
}
}
}
return 0;
}
void main()
{
time_t start, end;
start = time(NULL);
printf("Enter the value of N for NxN chessboard\n");
scanf("%d", &N);
int i, j;
for (i = 0; i < N; i++)
{
for (j = 0; j < N; j++)
{
board[i][j] = 0;
}
}
N_queen(N);
for (i = 0; i < N; i++)
{
for (j = 0; j < N; j++)
printf("%d\t", board[i][j]);
printf("\n");
}
end = time(NULL);
printf("\n Time taken by program is %.2f seconds", difftime(end, start));
}