bitmap解八皇后问题

 1 void backtracking(int row, int n, int left, int right, int col, int &count)
 2 {
 3     if (row == n)
 4     {
 5         count++;
 6     }
 7     int bits = (~(col | left | right))&((1 << n) - 1);
 8 
 9     while (bits)
10     {
11         int bit = -bits & bits;
12         backtracking(row + 1, n, (left | bit) << 1, (right | bit) >> 1, col | bit, count);
13         bits = bits ^ bit;
14     }
15 }
16 int totalNQueens(int n) {
17     int count = 0;
18     backtracking(0,n,0,0,0,count);
19     return count;
20 }