题解 | n皇后问题

class Queens {
    int count=0;
    void solve(int n, int row, int col, int ld, int rd ){
        if(row ==n ){
            ++count;
            return ;
        }
        int available = ((1<<n) -1) & ~( col | ld | rd);
        while (available) {
        int pos = available & -available;
        available -= pos;
        solve(n, row+1, col | pos, (ld | pos) <<1, (rd | pos)>>1);
        }
    }
public:
    int nQueens(int n) {
        // write code here
        solve(n, 0, 0, 0, 0);
        return count;
    }
};