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  1. #define N 4
  2. #include <stdbool.h>
  3. #include <stdio.h>
  4.  
  5. void printSolution(int board[N][N])
  6. {
  7.     for (int i = 0; i < N; i++) {
  8.         for (int j = 0; j < N; j++)
  9.             printf(" %d ", board[i][j]);
  10.         printf("\n");
  11.     }
  12. }
  13.  
  14. bool isSafe(int board[N][N], int row, int col)
  15. {
  16.     int i, j;
  17.  
  18.     for (i = 0; i < col; i++)
  19.         if (board[row][i])
  20.             return false;
  21.  
  22.     for (i = row, j = col; i >= 0 && j >= 0; i--, j--)
  23.         if (board[i][j])
  24.             return false;
  25.  
  26.     for (i = row, j = col; j >= 0 && i < N; i++, j--)
  27.         if (board[i][j])
  28.             return false;
  29.  
  30.     return true;
  31. }
  32.  
  33.  
  34. bool solveNQUtil(int board[N][N], int col)
  35. {
  36.  
  37.     if (col >= N)
  38.         return true;
  39.  
  40.     for (int i = 0; i < N; i++) {
  41.  
  42.         if (isSafe(board, i, col)) {
  43.  
  44.             board[i][col] = 1;
  45.  
  46.  
  47.             if (solveNQUtil(board, col + 1))
  48.                 return true;
  49.  
  50.  
  51.             board[i][col] = 0; 
  52.         }
  53.     }
  54.     return false;
  55. }
  56.  
  57. bool solveNQ()
  58. {
  59.     int board[N][N] = { { 0, 0, 0, 0 },
  60.                         { 0, 0, 0, 0 },
  61.                         { 0, 0, 0, 0 },
  62.                         { 0, 0, 0, 0 } };
  63.  
  64.     if (solveNQUtil(board, 0) == false) {
  65.         printf("Solution does not exist");
  66.         return false;
  67.     }
  68.  
  69.     printSolution(board);
  70.     return true;
  71. }
  72.  
  73.  
  74. int main()
  75. {
  76.     solveNQ();
  77.     return 0;
  78. }
  79.  
  80.  
Success #stdin #stdout 0.02s 26072KB
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#define N 4
#include <stdbool.h>
#include <stdio.h>

void printSolution(int board[N][N])
{
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++)
            printf(" %d ", board[i][j]);
        printf("\n");
    }
}
  
bool isSafe(int board[N][N], int row, int col)
{
    int i, j;
  
    for (i = 0; i < col; i++)
        if (board[row][i])
            return false;
  
    for (i = row, j = col; i >= 0 && j >= 0; i--, j--)
        if (board[i][j])
            return false;
  
    for (i = row, j = col; j >= 0 && i < N; i++, j--)
        if (board[i][j])
            return false;
  
    return true;
}
  

bool solveNQUtil(int board[N][N], int col)
{
    
    if (col >= N)
        return true;
  
    for (int i = 0; i < N; i++) {
        
        if (isSafe(board, i, col)) {
            
            board[i][col] = 1;
  
            
            if (solveNQUtil(board, col + 1))
                return true;
  
            
            board[i][col] = 0; 
        }
    }
    return false;
}
  
bool solveNQ()
{
    int board[N][N] = { { 0, 0, 0, 0 },
                        { 0, 0, 0, 0 },
                        { 0, 0, 0, 0 },
                        { 0, 0, 0, 0 } };
  
    if (solveNQUtil(board, 0) == false) {
        printf("Solution does not exist");
        return false;
    }
  
    printSolution(board);
    return true;
}
  

int main()
{
    solveNQ();
    return 0;
}
https://ideone.com/XCra7F
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1 year ago
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