leetcode - N-Queens II
Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.
class Solution { private: int res; public: int totalNQueens(int n) { std::vector<int> state(n, -1); res = 0; dfs(state, 0); return res; } void dfs(std::vector<int> &state, int row) { int n = state.size(); if(row == n) { res++; return; } for(int col = 0; col < n; col++) if(isValid(state, row, col)) { state[row] = col; dfs(state, row+1); state[row] = -1;; } } bool isValid(std::vector<int> &state, int row, int col) { for(int i = 0; i < row; i++) if(state[i] == col || abs(row - i) == abs(col - state[i])) return false; return true; } };
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