function - Using fgets and sscanf in C messed up the program after loop -

i'm programming tic tac toe game in c.

everything seems going okay, implement error handling techniques programs in case user inputs bad data.

i ask user input number between 1-9 fill slot on tic tac toe graph. when used fgets , sscanf together, ran during first game. then, when user selected 'y' or 'y' continue playing new game, seemed if none of variable values refreshed, , causing chaos within program.

any tips?

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <conio.h> int printmatch(int array[3][3]); int check(int array[3][3]); char y; char y; int complacer = 0; int complacer2 = 0;  int main() {     {      int fill = 0;     int j = 0;     int slot = 0;     int array[3][3];     array[0][0] = 0;     array[0][1] = 0;     array[0][2] = 0;     array[1][0] = 0;     array[2][0] = 0;     array[1][1] = 0;     array[2][1] = 0;     array[1][2] = 0;     array[2][2] = 0;     srand(time(null ));     printmatch(array);     char line[20];          {             {         tryagain: printf("\nenter position 1-9(from left right):");          //i using fgets , sscanf error handling technique incase user inputs incompatible data type, after 1st game over, seems code messes functionality of program         //fgets(line,sizeof(line),stdin);         //sscanf(line,"%d",&slot);          //when use scanf data input, fine, limited error handling         scanf("%d", &slot);         if (slot > 9 || slot < 1)         {           printf("incorrect data input! try again. \n");         }        } while (!(slot > 0 && slot < 10));        switch (slot)       {       case 1:         if (array[0][0] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[0][0] = 1;         check(array);         break;       case 2:         if (array[1][0] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[1][0] = 1;         check(array);         break;       case 3:         if (array[2][0] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[2][0] = 1;         check(array);         break;       case 4:         if (array[0][1] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[0][1] = 1;         check(array);         break;       case 5:         if (array[1][1] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[1][1] = 1;         check(array);         break;       case 6:         if (array[2][1] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[2][1] = 1;         check(array);         break;       case 7:         if (array[0][2] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[0][2] = 1;         check(array);         break;       case 8:         if (array[1][2] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[1][2] = 1;         check(array);         break;       case 9:         if (array[2][2] == -1)         {           printf("\nwoops, try again!");           goto tryagain;         }         array[2][2] = 1;         check(array);         break;        }        if (array[0][0] != 0 && array[0][1] != 0 && array[0][2] != 0           && array[1][0] != 0 && array[2][0] != 0 && array[1][1] != 0           && array[2][1] != 0 && array[1][2] != 0 && array[2][2] != 0)       {         check(array);          if (check(array) == 1)         {           printf("the user wins!\n");         }          else if (check(array) == -1)         {           printf("the computer wins.\n");         }          else         {           printmatch(array);           printf("it's draw!\n");         }          goto done;       }       ++fill;       label:        complacer = rand() % 3;       complacer2 = rand() % 3;        if (array[complacer][complacer2] == 0)       {         array[complacer][complacer2] = -1;         check(array);       }        else         goto label;        ++fill;        printmatch(array);       int fullcheck = check(array);       if (fullcheck == 1)       {         printf("the user wins!");         break;       }        if (fullcheck == -1)       {         printf("the computer wins.");         break;       }        if (fill > 9)         break;     } while (fill < 10);     done: printf("\ndo want continue? y/n\n");     scanf("%c %c", &y, &y);   } while ((y == 'y' || y == 'y'));   getchar();   return 0;  } int printmatch(int array[3][3]) {    int i;   int j;   (i = 0; < 3; i++)   {     (j = 0; j < 3; j++)     {       printf("%d\t", array[j][i]);     }      printf("\n");    } }  int check(int array[3][3]) {   int settle;    if (array[0][0] == 1 && array[1][1] == 1 && array[2][2] == 1)   {     settle = 1;    }    else if (array[0][0] == -1 && array[1][1] == -1 && array[2][2] == -1)   {      settle = -1;    }    if (array[0][0] == 1 && array[0][1] == 1 && array[0][2] == 1)   {     settle = 1;    }   else if (array[0][0] == -1 && array[0][1] == -1 && array[0][2] == -1)   {      settle = -1;    }    if (array[0][2] == 1 && array[1][2] == 1 && array[2][2] == 1)   {     settle = 1;    }   else if (array[0][2] == -1 && array[1][2] == -1 && array[2][2] == -1)   {      settle = -1;    }    if (array[0][1] == 1 && array[1][1] == 1 && array[2][1] == 1)   {     settle = 1;    }   else if (array[0][1] == -1 && array[1][1] == -1 && array[2][1] == -1)   {      settle = -1;    }    if (array[1][0] == 1 && array[1][1] == 1 && array[1][2] == 1)   {     settle = 1;    }   else if (array[1][0] == -1 && array[1][1] == -1 && array[1][2] == -1)   {     settle = -1;    }    if (array[0][0] == 1 && array[1][0] == 1 && array[2][0] == 1)   {     settle = 1;    }   else if (array[1][0] == -1 && array[1][1] == -1 && array[1][2] == -1)   {     settle = -1;    }    if (array[2][0] == 1 && array[1][1] == 1 && array[0][2] == 1)   {     settle = 1;    }   else if (array[1][0] == -1 && array[1][1] == -1 && array[1][2] == -1)   {     settle = -1;    }   if (array[2][0] == 1 && array[2][1] == 1 && array[2][2] == 1)   {     settle = 1;    }    else if (array[2][0] == -1 && array[2][1] == -1 && array[2][2] == 1)   {     settle = -1;    }   return settle; } 

user input evil. when want number, types 'a'. want 'y' or 'n' , input of dozens of letters. kudos trying improve coding defensive error handling.

when using sscanf() or scanf(), etc., sure check results

int result;   result = sscanf(buffer, "%this %that ...", &var1);   if (result != expectedresult) // handle error 

mixing fgets() getchar() , scanf() confuse issue. recommend not using fgets() 2. fgets() line orientated, scanf() stops before consuming new-line.

its fun type 'y' or 'y' continue, using "letter & enter_key" combo not bad , easier sort out @ first.

the fgets() sscanf() pair may have caused hiccup, in end easier sort out. recommend returning style , checking result of sscanf().

example

scanf("%d", &slot); 

here not know if user typed number before pressing 'enter'. user did type number, scanf() consumes leading spaces , digits, leaves 'enter' next input function. instead:

int scancount; const char *prompt = "\nenter position 1-9(from left right):"; {   fputs(prompt, stdout);   prompt = "incorrect data input! try again. \n"; // maybe next time around   if (fgets(line, sizeof(line), stdin) == null) {     // standard input closed or grievous i/o error, let's go home.     return 0;   }   scancount = sscanf(line,"%d",&slot); } while ((scancount != 1) || (slot < 1) || slot > 9)); 

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btw: here little trick test if extra text entered after number "9z". replace scancount = ... slot > 9)); with

char c; scancount = sscanf(line,"%d%[^\n]",&slot, &c); } while ((scancount != 1) || (slot < 1) || slot > 9));  // still scancount != 1