#include <stdio.h>
                                                //program to replace repeated numbers with whitespace without changing positions of numbers
char   copy(char c);                            //to create a copy of file.txt to check duplicates
int    find(int *pos);                          //to find and return numbers
int    numofdig(int n);
int    overwrite(int ow);                       //to replace duplicate numbers with whitespace

int main(){                   
    int             val1 = 0, val2 =1;
    int             loc,dig;                    //to store where scanning was left
    char            c;                          //to create a duplicate text file to check
    FILE            *fp1, *fp2;                 //file pointers

    fp1 =  fopen("file.txt","r+");              //opening files
    fp2 =  fopen("abc.txt","w+");

    copy(c);                                    //run copy function
    val1 = find(&loc);                          //run find function
    printf("%d,%d,%d\n",val1,loc,&loc);
    dig=numofdig(val1);                         //find number of digits 
    loc=loc-dig;                                //return back to position of number start
    overwrite(loc);                             //overwrite function
    
    fclose(fp1);                                //closing files
    fclose(fp2);
}

char copy(char c){                              //copy function
FILE            *fp1, *fp2;

fp1 =  fopen("file.txt","r+");                  //opening files
fp2 =  fopen("abc.txt","r+");

c = fgetc(fp1);                                 //creating duplicate of file.txt
    while (c != EOF)
    {
        fputc(c, fp2);                                    
        c = fgetc(fp1);
    }
fclose(fp1);                                    //closing files
fclose(fp2);
}

int find(int *pos){
    int val=0, val1, val2;                      //declaring integers for the function
    FILE *fp1, *fp2;                            //fiile pointers
    fp1 = fopen("abc.txt", "r");                //opening files
    fp2 = fopen("file.txt", "r");
    while((fscanf(fp1, "%d", &val)) != EOF){    //a loop to look for a meaningful number,
                                                //while skipping whitespace
        if(val == ' ')  continue;
        else val1 = val;
        if(val != ' ') break;
        
    }

    *pos = ftell(fp1);                          //taking the current position via ftell function
    val = 0;

    fseek(fp2, *pos, SEEK_SET);                 //using fseek to navigate in the file and skip 
    while((fscanf(fp2, "%d", &val)) != EOF){    //to look where scanning was left, 
        if(val == ' ')  continue;               //meanwhile looking if there is a repeating number
        else val2 = val;
        if(val1 == val2) break;
    }
    *pos = ftell(fp2);                          //updating the position

    fclose(fp1);                                //closing files
    fclose(fp2);

    if(val1 == val2) return val1;               //returning value
    else return -1;
}

int numofdig(int n){                            //a simple function to get digits of a number
int counter=0; 
    while(n!=0)  
    {  
        n=n/10;  
        counter++;  
    }  
    return counter;
}

int overwrite(int ow){                          //function to overwrite when repeating numbers are found
char a;
FILE *fp;
fp = fopen("file.txt", "w+");
fseek(fp, ow, SEEK_SET);
while((a=fgetc(fp)) != EOF && (a != 32))
    fputc(32,fp);
    
fclose(fp);

}