[leetcode]Sudoku Solver

Sudoku Solver

Total Accepted: 4129 Total
Submissions: 20589My Submissions

Write a program to solve a Sudoku puzzle by filling the empty cells.
Empty cells are indicated by the character

'.'

.
You may assume that there will be only one unique solution.



A sudoku puzzle...



本题用回溯法（递归），检查每个格子，如果是‘.’ 用1到9 依次带入试验，
比如带入‘1’时，如果（isValid）&&（solve）为true 说明可行，不可行的话复位‘.’

class Solution {
public:
void solveSudoku(vector<vector<char> > &board) {
solve(board);
}
bool solve(vector<vector<char> > &board){
for(int i=0; i<9; i++){
for(int j=0; j<9; j++){
if(board[i][j]=='.'){
for(char now='1'; now<='9';now++){
board[i][j]=now;
if(isValid(board,i,j) && solve(board))
return true;
else
board[i][j]='.';
}
return false;
}
}
}
return true;
}
bool isValid(vector<vector<char>> &board, int row, int col){
for(int j=0; j<9; j++){//检查所在行
char checkch=board[row][j];
if(j!=col  && checkch==board[row][col] )
return false;
}
for(int i=0; i<9; i++){//检查所在列
char checkch=board[i][col];
if(i!=row  && checkch==board[row][col])
return false;
}
for(int i=(row/3)*3; i<(row/3)*3+3; i++){
for(int j=(col/3)*3; j<(col/3)*3+3; j++){
char checkch=board[i][j];
if(i!=row && j!=col && checkch==board[row][col])
return false;
}
}
return true;
}
};