This piece of code is part of a large source code but the bug

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Asked: May 22, 20262026-05-22T11:56:00+00:00 2026-05-22T11:56:00+00:00

This piece of code is part of a large source code but the bug

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This piece of code is part of a large source code but the bug is here.

int solve(int* unsolved_var)
{
        int i;
        for (i = 0; unsolved_var[i] != 0; i++)
        {
            int n;
            for (n = 1; n <= 9; n++)
            {
                 //if (!numInBox(unsolved_var[i], n)==1 || !numInLine()==1)

                 printf("%d  %d\n", n,  unsolved_var[i]);
         numInBox(unsolved_var[i], n);//ERROR OCCURS HERE
            }
        }
}

int numInBox(int space, int n)//space is always three digits long
{
   printf("this should print but doesnt(segmentation fault)");
   char unsolved_str[3];
   sprintf(unsolved_str, "%d", space);//converts int into char[]

   printf("%s",unsolved_str);//confirms

   int check[3] = {atoi(unsolved_str[0]), 0, atoi(unsolved_str[2])};//converts char[] to int[]

Complete Code…its long it runs fine thou. If you type in solve then ill throw you that error.

`#include <stdio.h>
#include <string.h>

char grid[20][42];

void display()
{
        int j;
    int u;
    for (j = 0; j <= 19; j++)
    {
        for (u = 0; u <= 39; u++)
        {
            printf("%c",grid[j][u]);
        }
        printf("\n");
    }
    printf("\n");
}

int* unsolved()
{//2-18 4,8-36
int r;
int c;
   int size = 0;
   static int unsolved_var[81];
   unsolved_var[0] = 0;
   for (r = 2; r <= 18; r+=2)
   {
       for (c = 4; c <=36; c+=4)
       {
           if (grid[r][c] == ' ')
           {
           if (c <= 9)
               {
                   unsolved_var[size] = r/2*100 + c/4;
                   size++;
                   unsolved_var[size] = 0;//sets end of array
               }
               else
               {
                   unsolved_var[size] = r/2*100 + c/4;
                   size++;
                   unsolved_var[size] = 0;
               }
        // 100   1000    100   1000
            //2-0-4 2-0-10 10-0-4 10-0-10
           }
       }
   }
int p;
//for (p = 0; p <= size; p++){printf("%d", unsolved_var[p]);}
return unsolved_var;
}

int numInBox(int space, int n)
{
   char unsolved_str[3];
   sprintf(unsolved_str, "%d", space);

   printf("%s",unsolved_str);

   int check[3] = {atoi(unsolved_str[0]), 0, atoi(unsolved_str[2])};

}//***********************************************************************

static int x = 0;
int solve(int* unsolved_var)
{
   if (unsolved_var[0] == 0 || x == 10){return 0;}
   else
   {
        int i;
        for (i = 0; unsolved_var[i] != 0; i++)
        {
            int n;
            for (n = 1; n <= 9; n++)
            {
                 //if (!numInBox(unsolved_var[i], n)==1 || !numInLine()==1)

                 printf("%d  %d\n", n,  unsolved_var[i]);//
         numInBox(unsolved_var[i], n);
            }
        }
    x++;
   }
}

main()
{
//*****************************GRID******************************
//2 4 6 8 10 12 14 16 18
//3-5 7-9 11-13 15-17 19-21 23-25 27-29 31-33 35-37
        char top[] =   "\t  1   2   3   4   5   6   7   8   9  ";
    char line0[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field1[]="1\t|   |   |   |   |   |   |   |   |   |";
    char line1[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field2[]="2\t|   |   |   |   |   |   |   |   |   |";
    char line2[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field3[]="3\t|   |   |   |   |   |   |   |   |   |";
    char line3[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field4[]="4\t|   |   |   |   |   |   |   |   |   |";
    char line4[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field5[]="5\t|   |   |   |   |   |   |   |   |   |";
    char line5[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field6[]="6\t|   |   |   |   |   |   |   |   |   |";
    char line6[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field7[]="7\t|   |   |   |   |   |   |   |   |   |";
    char line7[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field8[]="8\t|   |   |   |   |   |   |   |   |   |";
    char line8[] = "\t+---+---+---+---+---+---+---+---+---+";
    char field9[]="9\t|   |   |   |   |   |   |   |   |   |";
    char line9[] = "\t+---+---+---+---+---+---+---+---+---+";

        int o;
        for (o = 0; o <= 39; o++)
        {
            grid[0][o] = top[o];
        grid[1][o] = line0[o];
        grid[2][o] = field1[o];
        grid[3][o] = line1[o];
        grid[4][o] = field2[o];
        grid[5][o] = line2[o];
        grid[6][o] = field3[o];
        grid[7][o] = line3[o];
        grid[8][o] = field4[o];
        grid[9][o] = line4[o];
        grid[10][o] = field5[o];
        grid[11][o] = line5[o];
        grid[12][o] = field6[o];
        grid[13][o] = line6[o];
        grid[14][o] = field7[o];
        grid[15][o] = line7[o];
        grid[16][o] = field8[o];
        grid[17][o] = line8[o];
        grid[18][o] = field9[o];
        grid[19][o] = line9[o];
        }
    display();
//****************************INPUT******************************
while(1)
{
  char input_raw[7];
  printf("Enter a Command\n");
  fgets(input_raw, 256, stdin);
  input_raw[strlen(input_raw)-1] = '\0';

if (strcmp(input_raw, "solve") == 0){solve(unsolved());}
else
{
  char *first = input_raw;
  char *second = input_raw; 
  char *third = input_raw;

  char *copy = input_raw;

  int flag = 1;
  while (*copy) 
  {
    if (*copy == ',') 
    {
      *copy = '\0'; 
      if (flag==0) {third = ++copy;}
      if (flag==1) {second = ++copy; flag = 0;}

    }
    else copy++;
  }

  switch (first[0])
  {
      case '1':
      {
          switch (second[0])
          {
              case '1':{grid[2][3] = '*'; grid[2][4]=third[0]; grid[2][5] = '*'; break;}
              case '2':{grid[2][7] = '*'; grid[2][8]=third[0]; grid[2][9] = '*'; break;}
              case '3':{grid[2][11] = '*';grid[2][12]=third[0];grid[2][13] = '*';break;}
              case '4':{grid[2][15] = '*';grid[2][16]=third[0];grid[2][17] = '*';break;}
              case '5':{grid[2][19] = '*';grid[2][20]=third[0];grid[2][21] = '*';break;}
              case '6':{grid[2][23] = '*';grid[2][24]=third[0];grid[2][25] = '*';break;}
              case '7':{grid[2][27] = '*';grid[2][28]=third[0];grid[2][29] = '*';break;}
              case '8':{grid[2][31] = '*';grid[2][32]=third[0];grid[2][33] = '*';break;}
              case '9':{grid[2][35] = '*';grid[2][36]=third[0];grid[2][37] = '*';break;}
          }
          break;
      }
      case '2':
      {
          switch (second[0])
          {
              case '1':{grid[4][3] = '*'; grid[4][4]=third[0]; grid[4][5] = '*'; break;}
              case '2':{grid[4][7] = '*'; grid[4][8]=third[0]; grid[4][9] = '*'; break;}
              case '3':{grid[4][11] = '*';grid[4][12]=third[0];grid[4][13] = '*';break;}
              case '4':{grid[4][15] = '*';grid[4][16]=third[0];grid[4][17] = '*';break;}
              case '5':{grid[4][19] = '*';grid[4][20]=third[0];grid[4][21] = '*';break;}
              case '6':{grid[4][23] = '*';grid[4][24]=third[0];grid[4][25] = '*';break;}
              case '7':{grid[4][27] = '*';grid[4][28]=third[0];grid[4][29] = '*';break;}
              case '8':{grid[4][31] = '*';grid[4][32]=third[0];grid[4][33] = '*';break;}
              case '9':{grid[4][35] = '*';grid[4][36]=third[0];grid[4][37] = '*';break;}
          }
          break;
      }
      case '3':
      {
          switch (second[0])
          {
              case '1':{grid[6][3] = '*'; grid[6][4]=third[0]; grid[6][5] = '*'; break;}
              case '2':{grid[6][7] = '*'; grid[6][8]=third[0]; grid[6][9] = '*'; break;}
              case '3':{grid[6][11] = '*';grid[6][12]=third[0];grid[6][13] = '*';break;}
              case '4':{grid[6][15] = '*';grid[6][16]=third[0];grid[6][17] = '*';break;}
              case '5':{grid[6][19] = '*';grid[6][20]=third[0];grid[6][21] = '*';break;}
              case '6':{grid[6][23] = '*';grid[6][24]=third[0];grid[6][25] = '*';break;}
              case '7':{grid[6][27] = '*';grid[6][28]=third[0];grid[6][29] = '*';break;}
              case '8':{grid[6][31] = '*';grid[6][32]=third[0];grid[6][33] = '*';break;}
              case '9':{grid[6][35] = '*';grid[6][36]=third[0];grid[6][37] = '*';break;}
          }
          break;
      }
      case '4':
      {
          switch (second[0])
          {
              case '1':{grid[8][3] = '*'; grid[8][4]=third[0]; grid[8][5] = '*'; break;}
              case '2':{grid[8][7] = '*'; grid[8][8]=third[0]; grid[8][9] = '*'; break;}
              case '3':{grid[8][11] = '*';grid[8][12]=third[0];grid[8][13] = '*';break;}
              case '4':{grid[8][15] = '*';grid[8][16]=third[0];grid[8][17] = '*';break;}
              case '5':{grid[8][19] = '*';grid[8][20]=third[0];grid[8][21] = '*';break;}
              case '6':{grid[8][23] = '*';grid[8][24]=third[0];grid[8][25] = '*';break;}
              case '7':{grid[8][27] = '*';grid[8][28]=third[0];grid[8][29] = '*';break;}
              case '8':{grid[8][31] = '*';grid[8][32]=third[0];grid[8][33] = '*';break;}
              case '9':{grid[8][35] = '*';grid[8][36]=third[0];grid[8][37] = '*';break;}
          }
          break;
      }
      case '5':
      {
          switch (second[0])
          {
              case '1':{grid[10][3] = '*'; grid[10][4]=third[0]; grid[10][5] = '*'; break;}
              case '2':{grid[10][7] = '*'; grid[10][8]=third[0]; grid[10][9] = '*'; break;}
              case '3':{grid[10][11] = '*';grid[10][12]=third[0];grid[10][13] = '*';break;}
              case '4':{grid[10][15] = '*';grid[10][16]=third[0];grid[10][17] = '*';break;}
              case '5':{grid[10][19] = '*';grid[10][20]=third[0];grid[10][21] = '*';break;}
              case '6':{grid[10][23] = '*';grid[10][24]=third[0];grid[10][25] = '*';break;}
              case '7':{grid[10][27] = '*';grid[10][28]=third[0];grid[10][29] = '*';break;}
              case '8':{grid[10][31] = '*';grid[10][32]=third[0];grid[10][33] = '*';break;}
              case '9':{grid[10][35] = '*';grid[10][36]=third[0];grid[10][37] = '*';break;}
          }
          break;
      }
      case '6':
      {
          switch (second[0])
          {
              case '1':{grid[12][3] = '*'; grid[12][4]=third[0]; grid[12][5] = '*'; break;}
              case '2':{grid[12][7] = '*'; grid[12][8]=third[0]; grid[12][9] = '*'; break;}
              case '3':{grid[12][11] = '*';grid[12][12]=third[0];grid[12][13] = '*';break;}
              case '4':{grid[12][15] = '*';grid[12][16]=third[0];grid[12][17] = '*';break;}
              case '5':{grid[12][19] = '*';grid[12][20]=third[0];grid[12][21] = '*';break;}
              case '6':{grid[12][23] = '*';grid[12][24]=third[0];grid[12][25] = '*';break;}
              case '7':{grid[12][27] = '*';grid[12][28]=third[0];grid[12][29] = '*';break;}
              case '8':{grid[12][31] = '*';grid[12][32]=third[0];grid[12][33] = '*';break;}
              case '9':{grid[12][35] = '*';grid[12][36]=third[0];grid[12][37] = '*';break;}
          }
          break;
      }
      case '7':
      {
          switch (second[0])
          {
              case '1':{grid[14][3] = '*'; grid[14][4]=third[0]; grid[14][5] = '*'; break;}
              case '2':{grid[14][7] = '*'; grid[14][8]=third[0]; grid[14][9] = '*'; break;}
              case '3':{grid[14][11] = '*';grid[14][12]=third[0];grid[14][13] = '*';break;}
              case '4':{grid[14][15] = '*';grid[14][16]=third[0];grid[14][17] = '*';break;}
              case '5':{grid[14][19] = '*';grid[14][20]=third[0];grid[14][21] = '*';break;}
              case '6':{grid[14][23] = '*';grid[14][24]=third[0];grid[14][25] = '*';break;}
              case '7':{grid[14][27] = '*';grid[14][28]=third[0];grid[14][29] = '*';break;}
              case '8':{grid[14][31] = '*';grid[14][32]=third[0];grid[14][33] = '*';break;}
              case '9':{grid[14][35] = '*';grid[14][36]=third[0];grid[14][37] = '*';break;}
          }
          break;
      }
      case '8':
      {
          switch (second[0])
          {
              case '1':{grid[16][3] = '*'; grid[16][4]=third[0]; grid[16][5] = '*'; break;}
              case '2':{grid[16][7] = '*'; grid[16][8]=third[0]; grid[16][9] = '*'; break;}
              case '3':{grid[16][11] = '*';grid[16][12]=third[0];grid[16][13] = '*';break;}
              case '4':{grid[16][15] = '*';grid[16][16]=third[0];grid[16][17] = '*';break;}
              case '5':{grid[16][19] = '*';grid[16][20]=third[0];grid[16][21] = '*';break;}
              case '6':{grid[16][23] = '*';grid[16][24]=third[0];grid[16][25] = '*';break;}
              case '7':{grid[16][27] = '*';grid[16][28]=third[0];grid[16][29] = '*';break;}
              case '8':{grid[16][31] = '*';grid[16][32]=third[0];grid[16][33] = '*';break;}
              case '9':{grid[16][35] = '*';grid[16][36]=third[0];grid[16][37] = '*';break;}
          }
          break;
      }
      case '9':
      {
          switch (second[0])
          {
              case '1':{grid[18][3] = '*'; grid[18][4]=third[0]; grid[18][5] = '*'; break;}
              case '2':{grid[18][7] = '*'; grid[18][8]=third[0]; grid[18][9] = '*'; break;}
              case '3':{grid[18][11] = '*';grid[18][12]=third[0];grid[18][13] = '*';break;}
              case '4':{grid[18][15] = '*';grid[18][16]=third[0];grid[18][17] = '*';break;}
              case '5':{grid[18][19] = '*';grid[18][20]=third[0];grid[18][21] = '*';break;}
              case '6':{grid[18][23] = '*';grid[18][24]=third[0];grid[18][25] = '*';break;}
              case '7':{grid[18][27] = '*';grid[18][28]=third[0];grid[18][29] = '*';break;}
              case '8':{grid[18][31] = '*';grid[18][32]=third[0];grid[18][33] = '*';break;}
              case '9':{grid[18][35] = '*';grid[18][36]=third[0];grid[18][37] = '*';break;}
          }
          break;
      }
  }
}
display();
}
}

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1 Answer

Editorial Team · Answer 1 · 2026-05-22T11:56:01+00:00

Since printf() buffers, using it as an indicator of exactly what line your segmentation fault occurs on is not generally a good idea. In general, writes to stderr don’t buffer like they do to stdout, so if you are looking to see how far you’ve gotten before a crash, you should do something more like fprintf(stderr, "Got Here before crash...\n");

That being said, your real problem is in the line

int check[3] = {atoi(unsolved_str[0]), 0, atoi(unsolved_str[2])};

If you look at your compiler warnings, you should be seeing something like:

warning: passing argument 1 of ‘atoi’ makes pointer from integer without a cast
/usr/include/stdlib.h:148: note: expected ‘const char *’ but argument is of type ‘char’

You need to re-write that line so that you’re passing constant pointers to char to atoi(), not objects of type char. So try this by adding an address-of operator:

int check[3] = {atoi(&unsolved_str[0]), 0, atoi(&unsolved_str[2])};

That will now pass the proper pointer type that atoi is expecting.

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