leetcode 127: N-Queens II
2013-04-05 16:39
127 查看
N-Queens
IIMar
20 '12
Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions. A good optimization example: when the request result is simplified, we may use reduced data struct to save time and space.
![](http://www.leetcode.com/wp-content/uploads/2012/03/8-queens.png)
won't pass the big dataset until use one dimension array to replace the matrix in queen I.
IIMar
20 '12
Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions. A good optimization example: when the request result is simplified, we may use reduced data struct to save time and space.
![](http://www.leetcode.com/wp-content/uploads/2012/03/8-queens.png)
won't pass the big dataset until use one dimension array to replace the matrix in queen I.
class Solution { public: int totalNQueens(int n) { // Start typing your C/C++ solution below // DO NOT write int main() function vector<int> board(n, -1); int sum = 0; queenRec(board, 0, sum); return sum; } private: void queenRec(vector<int>& board, int level, int & sum) { int n = board.size(); if(level==n) { ++sum; return; } for(int i=0; i<n; i++) { if(check(board, level, i)) { board[level] = i; queenRec(board, level+1, sum); board[level] = -1; } } } bool check(const vector<int>& cur, int row, int col) { int n= cur.size(); for(int i=0; i<row; i++) { if(cur[i]==col || row-i == abs(col-cur[i]) ) return false; } return true; } };
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