51(N皇后问题)
class Solution { public: vector<bool> col, dia1, dia2; vector<vector<string>> res; void putQueen(int n, int index, vector<int> &row){ if(index == n){ res.push_back(generateBoard(n, row)); return; } for(int i = 0 ; i < n ; i ++) if(!col[i] && !dia1[index + i] && !dia2[index - i + n - 1]){ row.push_back(i); col[i] = true; dia1[index + i] = true; dia2[index - i + n - 1] = true; putQueen(n, index + 1, row); col[i] = false; dia1[index + i] = false; dia2[index - i + n - 1] = false; row.pop_back(); } return; } vector<string> generateBoard(int n, vector<int> &row){ assert(row.size() == n); vector<string> board(n, string(n, '.')); for(int i = 0 ; i < n ; i ++) board[i][row[i]] = 'Q'; return board; } vector<vector<string>> solveNQueens(int n) { res.clear(); col.clear(); for(int i = 0 ; i < n ; i ++) col.push_back(false); dia1.clear(); dia2.clear(); for(int i = 0 ; i < 2 * n - 1 ; i ++){ dia1.push_back(false); dia2.push_back(false); } vector<int> row; putQueen(n, 0, row); return res; } };
52
37(求解数独)