C program to find out if a solved Sudoku is valid or invalid.

Object of this program is to find out if a solved Sudoku is valid or invalid.

/* when the program encounters "break;" statement, execution will come out of the innermost loop in which it present. */

Program:

#include<stdio.h>
int main()
{
         int a[9][9];
         int i,j,sum,temp,flag=1;
         printf("\n enter input::\n");
         for(i=0;i<9;i++){
             for(j=0;j<9;j++){
                  scanf("%d",&temp);
                  if(temp>0 && temp<10)          /*   check for valid input for Sudoku   */
                  a[i][j]=temp;
                  else{                               /* if any element is not invalid then successive breaks  */
                        flag=0;                             
                        printf(" invalid input ");
                        break;
                      }
             }
             if(flag==0)
             break;
         }
          if(flag)             /* if every input is in valid range then go for validation of Sudoku  */
         {
               for(i=0;i<9;i++)
               {
                    sum=0;
                    for(j=0;j<9;j++)
                    sum=sum+a[i][j];
                    if(sum!=45)
                       break;            /*   if sum is not 45 in any row then  go out of for loop  */
               }
               if(sum==45)                /*  if sum is 45 in all rows then check for columns   */
               {
                     for(i=0;i<9;i++)
                    {
                          sum=0;
                          for(j=0;j<9;j++)
                          sum=sum+a[j][i];
                          if(sum!=45)           
                          break;        /*   if sum is not 45 in any column then  go out of for loop  */
                    }
                    if(sum==45)                              /* if sum is 45 in all columns too    */
                       printf("Valid");
                    else printf("invalid");
               }
               else
                   printf("\n Invalid");
         }
         return 0;
}


Sample input:

1 9 4 8 7 5 6 2 3
8 5 3 9 6 2 4 7 1
2 6 7 3 1 4 9 8 5
9 2 1 6 5 8 7 3 4
6 7 8 4 3 1 2 5 9
4 3 5 2 9 7 8 1 6
5 8 6 7 4 3 1 9 2
3 4 2 1 8 9 5 6 7
7 1 9 5 2 6 3 4 8

Output:

Valid