[LeetCode] N-Queens II
Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.
思路:与http://www.cnblogs.com/vincently/p/4714230.html思路相同。
class Solution { public: int result; int queen_num_; int totalNQueens(int n) { result = 0; vector<int> a(n, -1); queen_num_ = n; solveNQueens(a); return result; } bool IsValid(const vector<int>& a, int row, int col) { for (int i = 0; i < row; i++) { if (col == a[i] || abs(i - row) == abs(a[i] - col)) return false; } return true; } void solveNQueens(vector<int>& a) { int i = 0, j = 0; while (i < queen_num_) { while (j < queen_num_) { if (IsValid(a, i, j)) { a[i] = j; j = 0; break; } else { j++; } } if (a[i] == -1) { if (i == 0) { return; } else { i--; j = a[i] + 1; a[i] = -1; continue; } } if (i == queen_num_ - 1) { result++; j = a[i] + 1; a[i] = -1; continue; } i++; }//while (i < queen_num_); }//solveNQueens };