Program to Check Whether Given Sudoku Solution Valid or Not

This program will Check whether the given Sudoku Solution is Valid Or Not .

Input :

Output :

Logic To Check for Valid Solution of Sudoku :

• • Get the Sudoku Solution from the user and store them in 2-Dimensinal integer Array .
  • Using another integer array store the count of each digits entered .
  • If the entered number is not between 1 to 9 again ask for the input .
  • A Valid Sudoku must satisfies the Following Conditions :
    1. Count of each digit entered must be Exactly 9 .
    2. All the 9 Rows and 9 Column Elements Sum should be Exactly 45 .
    3. Also the 9 , 3×3 Sub-matrix Sum of Elements Should be Exactly 45 .
  • The Reason for 45 is Sum of 1 to 9 is 45 . (1+2+3+4+5+6+7+8+9=45)
  • If the given Sudoku Solution Satisfies the Above three conditions then the Given Sudoku Solution is Valid .
  • If the Sudoku Solution fails to Satisfies any one of above three Conditions then the Solution is Invalid .
    

Program :

#include<iostream>
using namespace std;
int main()
{
  int a[9][9],c[9];			//a=sudoku_values,c=count_of_each_numbers
  int w=0;			        //w=used as flag variable
  cout<<"Enter the Sudoku Values One-By-One :";
  for(int i=0;i<9;i++)	      //this for loop is used to get sudoku values
  {
    for(int j=0;j<9;j++)
    {
      INPUT:
      char t;
      cin>>t;
      int temp=t-48;
      if(temp>0&&temp<10)     //if number is not between 1 to 9 then again number is asked
      {
        a[i][j]=temp;
        switch(temp)          //this switch statement counts each digits entered and store them in c[]
        {
          case 1:
                c[temp-1]=c[temp-1]+1;
                break;
          case 2:
                c[temp-1]=c[temp-1]+1;
                break;
          case 3:
                c[temp-1]=c[temp-1]+1;
                break;
          case 4:
                c[temp-1]=c[temp-1]+1;
                break;
          case 5:
                c[temp-1]=c[temp-1]+1;
                break;
          case 6:
                c[temp-1]=c[temp-1]+1;
                break;
          case 7:
                c[temp-1]=c[temp-1]+1;
                break;
          case 8:
                c[temp-1]=c[temp-1]+1;
                break;
          case 9:
                c[temp-1]=c[temp-1]+1;
                break;
        }
      }
      else
      {
        cout<<"Enter Between 1-10 !";
        goto INPUT;
      }
    }
  }
  //if all the digits entered is not have exact count of 9
  //then the sudoku is not valid
  for(int i=0;i<9;i++)
  {
    if(c[i]!=9)
    {
      cout<<"Sudoku is Invalid!";
      w=1;
      break;
    }
  }
  //the following for loop is used to count sum of both
  //horizontal and vertical direction
  if(w==0)
  {
    for(int i=0;i<9;i++)
    {
      int sh=0,sv=0;    //sh=sum_horizontal,sv=sum_vertical
      for(int j=0;j<9;j++)
      {
        sh=sh+a[i][j];
        sv=sv+a[j][i];
      }
      if(sh!=45||sv!=45)    //if sum is not exactly 45 then sudoku is invalid
      {
        cout<<"Sudoku is Invalid!";
        w=1;
        break;
      }
    }
  }
  //this following for loops finds the sum of all 3x3 sub matrices
  if(w==0)
  {
    for(int vc=0;vc<3;vc++)
    {
      for(int hc=0;hc<3;hc++)
      {
        int ssm=0;     //ssm=sum_sub_matrix
        for(int i=0;i<3;i++)
        {
          for(int j=0;j<3;j++)
          {
            ssm=ssm+a[(i+(vc*3))][(j+(hc*3))];
          }
          //cout<<"\n";
        }
        if(ssm!=45)      //if submatrix sum is not exactly 45 then sudoku is not valid
        {
          cout<<"Sudoku is Invalid!";
          w=1;
          break;
        }
      }
    }
  }
  //if value of flag w is unchanged then it satisfies all condition
  //so sudoku is valid
  if(w==0)       
  {
    cout<<"Sudoku is Valid !";
  }
  return 0;
}