nqueen_print_all_solutions.cpp

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#include <array>     
#include <iostream>  
 
namespace backtracking {
namespace n_queens_all_solutions {
template <size_t n>
void PrintSol(const std::array<std::array<int, n>, n>& board) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            std::cout << board[i][j] << " ";
        }
        std::cout << std::endl;
    }
    std::cout << std::endl;
}
 
template <size_t n>
bool CanIMove(const std::array<std::array<int, n>, n>& board, int row,
              int col) {
    for (int i = 0; i < col; i++) {
        if (board[row][i] == 1) {
            return false;
        }
    }
    for (int i = row, j = col; i >= 0 && j >= 0; i--, j--) {
        if (board[i][j] == 1) {
            return false;
        }
    }
    for (int i = row, j = col; i <= n - 1 && j >= 0; i++, j--) {
        if (board[i][j] == 1) {
            return false;
        }
    }
    return true;
}
 
template <size_t n>
void NQueenSol(std::array<std::array<int, n>, n> board, int col) {
    if (col >= n) {
        PrintSol(board);
        return;
    }
    for (int i = 0; i < n; i++) {
        if (CanIMove(board, i, col)) {
            board[i][col] = 1;
            NQueenSol(board, col + 1);
            board[i][col] = 0;
        }
    }
}
}  // namespace n_queens_all_solutions
}  // namespace backtracking
 
int main() {
    const int n = 4;
    std::array<std::array<int, n>, n> board{0};
 
    backtracking::n_queens_all_solutions::NQueenSol(board, 0);
}