Leetcode#52 N-Queens II

原题地址

 

跟N-Queens几乎没差别，好像还更简单了呢

 

代码：

 1 int solve(int row, vector<bool> &col, vector<bool> left, vector<bool> right) {

 2   if (row == 0)

 3     return 1;

 4 

 5   vector<bool> avail(col.size(), false);

 6   for (int i = 0; i < col.size(); i++)

 7     avail[i] = !(col[i] || left[i] || right[i]);

 8 

 9   for (int i = 0; i < col.size() - 1; i++)

10     left[i] = left[i + 1];

11   left[col.size() - 1] = false;

12   for (int i = col.size() - 1; i > 0; i--)

13     right[i] = right[i - 1];

14   right[0] = false;

15 

16   int res = 0;

17   for (int i = 0; i < col.size(); i++) {

18     if (!avail[i])

19       continue;

20     col[i] = true;

21     if (i > 0) left[i - 1] = true;

22     if (i < col.size() - 1) right[i + 1] = true;

23     res += solve(row - 1, col, left, right);

24     if (i < col.size() - 1) right[i + 1] = false;

25     if (i > 0) left[i - 1] = false;

26     col[i] = false;

27   }

28 

29   return res;

30 }

31 

32 int totalNQueens(int n) {

33   vector<bool> col = vector<bool>(n, false);

34   vector<bool> left = vector<bool>(n, false);

35   vector<bool> right = vector<bool>(n, false);

36   return solve(n, col, left, right);

37 }