332.重新安排行程

class Solution {
public:vector<string> result;bool backtracking(vector<vector<string>>& tickets, vector<bool>& used){if(result.size()==tickets.size()+1){return true;}for(int i=0; i<tickets.size(); i++){if(used[i] == true){continue;}if(tickets[i][0]==result.back()){result.push_back(tickets[i][1]);used[i] = true;if(backtracking(tickets, used)) return true;result.pop_back();used[i] = false;}}return false;}vector<string> findItinerary(vector<vector<string>>& tickets) {result.push_back("JFK");vector<bool> used(tickets.size(), false);backtracking(tickets, used);return result;}
};

参考文章：代码随想录-332.重新安排行程

51. N皇后

class Solution {
public:vector<vector<string>> result;bool isValid(int col, int row, vector<string>& temp, int n){for(int i=0; i<row; i++){if(temp[i][col]=='Q') return false;}for(int i=row-1, j=col-1; i>=0&&j>=0; i--, j--){if(temp[i][j]=='Q') return false;}for(int i=row-1, j=col+1; i>=0&&j<n; i--, j++){if(temp[i][j]=='Q') return false;}return true;}void backtracking(int n, int row, vector<string>& temp){if(row == n){result.push_back(temp);return;}for(int i=0; i<n; i++){if(isValid(i, row, temp, n)){temp[row][i] = 'Q';backtracking(n, row+1, temp);temp[row][i] = '.';}}}vector<vector<string>> solveNQueens(int n) {result.clear();vector<string> temp(n, string(n, '.'));backtracking(n,0, temp);return result;}
};

参考文章：代码随想录- 51. N皇后

37. 解数独

class Solution {
public:bool isValid(int row, int col, char val, vector<vector<char>>& board){for(int i=0; i<board.size(); i++){if(board[i][col]==val){return false;}}for(int j=0; j<board.size(); j++){if(board[row][j]==val){return false;}}int row_s = (row/3)*3;int col_s = (col/3)*3;for(int i = row_s; i<row_s+3; i++){for(int j=col_s; j<col_s+3; j++){if(board[i][j]==val){return false;}}}return true;}bool backtracking(vector<vector<char>>& board){for(int i=0; i<board.size(); i++){for(int j=0; j<board.size(); j++){if(board[i][j] == '.'){for(char val='1'; val<='9'; val++){if(isValid(i,j,val, board)){board[i][j]=val;if(backtracking(board)) return true;board[i][j]='.';}}return false;}}}return true;}void solveSudoku(vector<vector<char>>& board) {backtracking(board);}
};

参考文章：代码随想录- 37. 解数独