leetcode 36. Valid Sudoku 37. Sudoku Solver

36. Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character 

'.'

.



A partially filled sudoku which is valid.

Note:

A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

判断一个数独盘的已经填上的部分是不是有效的数独盘。不需要判断没填上的部分。也就是看有没有重复的。

class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board)
{
map<char,int> m2;
//判断每一横排
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
if (board[i][j] == '.')
continue;
if (m2.find(board[i][j]) == m2.end())
m2[board[i][j]]++;
else
return false;
}
m2.clear();
}

//判断每一竖排
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
if(board[j][i]=='.')
continue;
if(m2.find(board[j][i])==m2.end())
m2[board[j][i]]++;
else
return false;
}
m2.clear();
}
//判断每一个九宫格
for(int k = 0; k < 3; k++)  //k控制 i的范围
{
for(int h = 0; h < 3; h++)    //h控制 j的范围
{
for(int i = k * 3; i < k * 3 + 3; i++)
{
for(int j = h * 3; j < h * 3 + 3; j++)
{
if(board[i][j]=='.')
continue;
if(m2.find(board[i][j]) == m2.end())
m2[board[i][j]]++;
else
return false;
}
}
m2.clear();
}
}
return true;
}
};

37. Sudoku Solver

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...



...and its solution numbers marked in red.

填数独

用递归的思想，先判断每一个空位可以填哪些，然后填进去再递归。

class Solution {
public:
int shudu(vector<vector<char>>&board,vector<vector<int>> &mm,int pos,int flag)
{
if (pos == mm.size())
return 1;

int a[10] = {0};
int x = mm[pos][0]; //需要填的位置
int y = mm[pos][1];
for(int i = 0; i < 9; i++)
{
if (board[x][i] != '.')//横
a[(int(board[x][i])-48)] = 1;
if (board[i][y] != '.')//竖
a[(int(board[i][y])-48)] = 1;
}
//3*3
for (int k = (x/3)*3; k < (x/3)*3+3; k++)
{
for(int h = (y/3)*3; h<(y/3)*3+3; h++)
{
if(board[k][h]!='.')
a[(int(board[k][h])-48)] = 1;
}
}
//把可以加的加进去
for(int i = 1; i <= 9; i++)
{
if(a[i] == 0)
{
board[x][y] = char(i+48);
flag = shudu(board,mm,pos+1,flag);
if(flag == 0)   // 填入之后递归失败
board[x][y] = '.';
else            // 填入之后递归成功
break;
}
}
return flag;
}

void solveSudoku(vector<vector<char>>& board)
{
//将点('.')的位置存起来
vector<vector<int>> mm;
vector<int> m1;
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
if (board[i][j] == '.')
{
m1.push_back(i);
m1.push_back(j);
mm.push_back(m1);
m1.clear();
}
}
}
//开始遍历
int k = shudu(board, mm, 0, 0);
}
};