C ile sudoku

#include <stdio.h> //////////////SUDOKU
#include <stdlib.h>


int main(int argc, char *argv[]) {
	char sudoku[4][4]={{'?','2','4','?'},{'1','?','?','3'},{'4','?','?','2'},{'?','1','3','?'}};
	int i,j,a;
	char k,x;
	int b[4]={'1','2','3','4'};
	for(i=0;i<4;i++){
		for(j=0;j<4;j++){
		printf("%c   ",sudoku[i][j]);
	}
	printf("\n");
	}
      for(i=0;i<4;i++){	
	  for(j=0;j<4;j++){  
    if(sudoku[i][j]=='?'){
	printf("Enter %d row and %d col and number\n",i+1,j+1);
	scanf(" %c",&k);
	sudoku[i][j]=k;
}
}
}
	int counter=0;
	int counterr=0;
		for(i=0;i<4;i++){
		for(j=0;j<4;j++){
		if(sudoku[i][0]==b[j]&&sudoku[0][i]==b[j]&&(sudoku[i][j]==!sudoku[j][i])) {
		counter++;
		}
	}
	}
		for(i=0;i<4;i++){
		for(j=0;j<4;j++){
		printf("%c   ",sudoku[i][j]);
	}
	printf("\n");
	}
	if (counter==8){
		printf("Congratulation");
	}
	else printf("Wrong");
	
	return 0;
}