#include <stdio.h>

#include<string.h>

#include<math.h>

#include<stdlib.h>

#include<unistd.h>

#include<malloc.h>

#include<time.h>

#define MAXSIZE 100

void initBoard(int* b,int n);

void printBoard(int* a,int n);

int generateRandomNum();

int solveNQueensUtil(int* b,int i);

void solveNQueens(int n);

int isSafe(int* b,int i,int j);

void clearRow(int* b,int i);

int isSafe(int* b,int i,int j)

{

int row4=i;

int col4=j;

int k=0;

while(k<8)

{

if(*(b+8*4*k+j)==1)

return 0;

k++;

}

int row1=i;

int col1=j;

int row2=i;

int col2=j;

int row3=i;

int col3=j;

int flag;

while(1)

{

flag=0;

row1++;

row2++;

row3--;

row4--;

col1++;

col2++;

col3--;

col4--;

if(row1<8 && col1<8)

{

flag=1;

if(*(b+8*4*row1+col1)==1)

return 0;

}

if(row2<8 && col3>-1)

{

flag=1;

if(*(b+8*4*row2+col3)==1)

return 0;

}

if(row3>-1 && col4>-1)

{

flag=1;

if(*(b+8*4*row3+col4)==1)

return 0;

}

if(row4>-1 && col2<8)

{

flag=1;

if(*(b+8*4*row4+col2)==1)

return 0;

}

if(flag==0)

break;

}

return 1;

}

int generateRandomNum()

{

time_t t;

srand((unsigned)time(0));

unsigned int random_integer;

int lowest = 0, highest = 7;

int range = (highest - lowest) + 1;

random_integer = lowest + (range * rand() / (RAND_MAX + 1.0));

return random_integer;

// return 2;

}

//void solveNQueens(int n);

void solveNQueens(int n)

{

int* board= (int*) malloc(64*4);

initBoard(board,8);

// int k=generateRandomNum();

printBoard(board,8);

if(solveNQueensUtil(board,0)==1)

{

printf("Solution Exists\n");

// printBoard(board,8);

}

else

printf("Solution doesn't exist\n");

printBoard(board,8);

}

int solveNQueensUtil(int* b,int i)

{

int k=generateRandomNum();

// printf("fe %d\n",i);

int j=k;

do

{

if(isSafe(b,i,j)==1 && *(b+8*4*i+j)!=1)

{

// printf("entering value at (%d,%d)\n",i,j);

// printf(" value at (0,6) is %d\n",*(b+8*4*0+6));

clearRow(b,i);

*(b+8*4*i+j)=1;

if(i==7)

return 1;

else

return solveNQueensUtil(b,i+1);

}

else if(*(b+8*4*i+j)==1 && isSafe(b,i,j)==0)

{

*(b+8*4*i+j)=0;

j++;

if(j==8)

j=0;

}

else

{

j++;

if(j==8)

j=0;

}

// j++;

}while(j!=k);

if(i>0)

return solveNQueensUtil(b,i-1);

return 0;

}

void clearRow(int* b,int i)

{

int j=0;

while(i<8)

{

*(b+4*8*i+j)=0;

i++;

}

}

int main()

{

int* board= (int*) malloc(64*4);

solveNQueens(8);

// initBoard(board,8);

// printBoard(board,8);

// solveNQueens(board);

return 0;

}

void initBoard(int* b,int n)

{

// int size=sizeof(b)/4;

int i,j;

int count=0;

for(i=0;i<8;i++)

{

// int* t;

// t=b;

for(j=0;j<8;j++)

{

*(b+8*4*i+j)=0;

// printf("%d", *(b+j));

//b++;

}

// b=b+4*(i+1);

// printf("%d",*(b));

// b++;

}

}

void printBoard(int* a,int n)

{

//int size=sizeof(a)/4;

int i=0;

int j;

for(i=0;i<8;i++)

{

for(j=0;j<8;j++)

{

//printf("---\n");

printf("| %d |",*(a+8*4*i+j));

}

// i++;

// if(i%n==0)

printf("\n");

}

}