closestKey.c

// Closest 64 bit integers to a given binary 64 bit integer,less than a distance of 4 will be sorted and printed 

//input line will have 0,1,2,232983293 .. keys
//input line2 is a 64 char binary 100100111010....11

//we print all keys that are within a max bit error of 4

#include<stdio.h>

#define STR_LEN 40000000
#define KEY_LEN 64


char key_list[STR_LEN]="";
char cmp_key[65]="";
char *key=NULL;

int
main(){

    char com[2] = ",";

    scanf("%s",&key_list); 
    scanf("%s",&cmp_key);

    key = strtok(key_list,com);
    while(key != NULL) {
      compare_keys(key);
      key = strtok(NULL,com);
    }

}




int
compare_keys(char *loc_key) {

     int il = KEY_LEN;
     char key_bin[65] = "0";
     unsigned long int i_tmp = strtoull(loc_key, (char **)NULL, 10);
     unsigned long int i = i_tmp;


     /* converting to binary */

     key_bin[il] = '\0';
     key_bin[il-1]=((i & 1) + '0');
     il--;
     while(il--) {
         i = i >> 1;
         key_bin[il]=((i & 1) + '0');
     }

     if(cmp_str(key_bin))
        printf("%d,",i_tmp);

}


int
cmp_str(char key_bin[]) {

   int i=0;
   int count=0;

   for(i=0 ; i <= 64 ; i++) {
      if(key_bin[i] != cmp_key[i])
           count++;

      if(count > 4)
          return 0;

   }
   return 1;
}


// (c) Alok Pepakayala