slow_queens.cpp

#include <iostream>
using namespace std;

int main() {
    int b[8][8] = {0}, r, c = 0;
    b[0][0] = 1;

    next_col:
    ++c;
    if (c == 8) { goto print; }
    r = -1;

    next_row:
    ++r;
    if (r == 8) { goto backtrack; }
    for (int i = 0; i < c; ++i) {
        if (b[r][i] == 1) { goto next_row; }
    }
    for (int i = 1; (r - i) >= 0 && (c - i) >= 0; ++i) {
        if (b[r - i][c - i] == 1) { goto next_row; }
    }
    for (int i = 1; (r + i) < 8 && (c - i) >= 0; ++i) {
        if (b[r + i][c - i] == 1) { goto next_row; }
    }
    b[r][c] = 1;
    goto next_col;

    backtrack:
    --c;
    if (c == -1) { return 0; }
    r = 0;
    while (b[r][c] != 1) {
        ++r;
    }
    b[r][c] = 0;
    goto next_row;

    print:

    for (int i = 0; i < 8; ++i) {
        for (int j = 0; j < 8; ++j) {
            cout << b[i][j];
        }
        cout << endl;
    }

    goto backtrack;
}