How do I find multiples values in binary search algorithm

Question

I want find many values in a binary search the problem is the binary search just find the first one and return it. Can I find as many I want? For example imagine that I have this input:

00001 1521065760 38 42' 50" -9 8' 22"
00001 1521066360 38 42' 4" -9 45' 24"
00001 1521066960 38 41' 18" -9 22' 26"
00001 1521067560 38 40' 32" -8 59' 28"
00001 1521068160 38 39' 46" -8 36' 30"
00001 1521068760 38 39' 2" -8 13' 32"
00001 1521069360 38 34' 0" -7 54' 0"
00001 1521069960 38 34' 0" -7 54' 0"
00002 1521065760 38 10' 33" -8 41' 35"
00002 1521066360 38 16' 14" -8 35' 36"
00002 1521066960 38 21' 55" -8 30' 20"
00002 1521067560 38 27' 36" -8 24' 44"
00002 1521068160 38 33' 17" -8 19' 8"
00002 1521068760 38 39' 2" -8 13' 32"
00002 1521069360 38 37' 16" -8 4' 50"
00002 1521069960 38 34' 0" -7 54' 0"

I want to find using binary search where 'codigos'(id) differents has the same input so it will be return this values(00001 and 00002):

   1521068760 38 39' 2" -8 13' 32"
   1521069960 38 34' 0" -7 54' 0"

This is my code:

#include <stdio.h>
#include <stdlib.h>
struct suspeito{
   int codigo;
   int instante;
   int graulatitude;
   int minutolatitude;
   int segundolatitude;
   int graulongitude;
   int minutolongitude;
   int segundolongitude;
   };

  int PesquisaBinaria(int n, struct suspeito informacao[], int i, int j)
   {
     if (i > j)
        return -1;                  // o intervalo i..j é vazio

    int m = (i + j) / 2;          // ponto médio do intervalo

    if (n < informacao[m].codigo)
        // restringe a pesquisa ao intervalo i..m - 1
         return PesquisaBinaria(n, informacao, i, m - 1);

    if (n > informacao[m].codigo)
          // restringe a pesquisa ao intervalo m + 1..j
         return PesquisaBinaria(n, informacao, m + 1, j);

      // n == v[m]
    return m;
          } 
    int compare(const void *p1, const void *p2)
    {
     const struct suspeito *elem1 = (struct suspeito *)p1;
     const struct suspeito *elem2 = (struct suspeito *)p2;
     if (elem1->codigo < elem2->codigo)
         return -1;
     else if (elem1->codigo > elem2->codigo)
         return 1;
     else
         return 0;
       }
   int main()
      {


      struct suspeito informacao[10000];
        int codigo,instante,graulatitude,minutolatitude,segundolatitude,graulongitude,minutolongitude,segundolongitude;
int count,par1,par2;
while(1) {
    scanf(" %d",&codigo);
    if(codigo==0) {
        break;
    }
    scanf(" %d %d %d\' %d\" %d %d\' %d\"",&instante,&graulatitude,&minutolatitude,&segundolatitude,&graulongitude,&minutolongitude,&segundolongitude);
    informacao[count].codigo=codigo;
    informacao[count].instante=instante;
    informacao[count].graulatitude=graulatitude;
    informacao[count].minutolatitude=minutolatitude;
    informacao[count].segundolatitude=segundolatitude;
    informacao[count].graulongitude=graulongitude;
    informacao[count].minutolongitude=minutolongitude;
    informacao[count].segundolongitude=segundolongitude;
    count++;
}
qsort(informacao,count,sizeof(informacao[0]),compare);
printf("Codigo: %d\nInstante: %d\n",informacao[3].codigo,informacao[3].instante);

if(codigo==00000) {
    while(scanf(" %d %d",&par1,&par2)!=EOF) {
            int find1=PesquisaBinaria(par1,informacao,0,count);
            int find2=PesquisaBinaria(par2,informacao,0,count);
            if(find1==-1 && find2!=-1)
                printf("+ sem dados sobre o suspeito %d",par1);
            if(find1!=-1 && find2==-1)
                printf("+ sem dados sobre o suspeito %d",par2);
            if(find1!=-1 && find2!=-1) {
                printf("Index1:%d \nIndex2:%d\n",find1-1,find2-1);
                printf("Codigo1:%d\nInstante1:%d\nGrauLatitude1:%d\nMinutoLatitude1:%d\nSegundoLatitude1:%d\nGrauLongitude1:%d\nMinutoLongitude1:%d\nSegundoLongitude1:%d\n",informacao[find1-1].codigo,informacao[find1-1].instante,informacao[find1-1].graulatitude,informacao[find1-1].minutolatitude,informacao[find1-1].segundolatitude,informacao[find1-1].graulongitude,informacao[find1-1].minutolongitude,informacao[find1-1].segundolongitude);
                printf("Codigo2:%d\nInstante2:%d\nGrauLatitude2:%d\nMinutoLatitude2:%d\nSegundoLatitude2:%d\nGrauLongitude2:%d\nMinutoLongitude2:%d\nSegundoLongitude2:%d\n",informacao[find2-1].codigo,informacao[find2-1].instante,informacao[find2-1].graulatitude,informacao[find2-1].minutolatitude,informacao[find2-1].segundolatitude,informacao[find2-1].graulongitude,informacao[find2-1].minutolongitude,informacao[find2-1].segundolongitude);
                if(informacao[find1-1].instante==informacao[find2-1].instante && informacao[find1-1].graulatitude == informacao[find2-1].graulatitude && informacao[find1-1].minutolatitude==informacao[find2-1].minutolatitude && informacao[find1-1].segundolatitude == informacao[find2-1].segundolatitude && informacao[find1-1].graulongitude==informacao[find2-1].graulongitude && informacao[find1-1].minutolongitude==informacao[find2-1].minutolongitude && informacao[find1-1].segundolongitude==informacao[find2-1].segundolongitude)
                    printf("+ %05d e %05d podem ter-se encontrado em:\n",par1,par2);

            }
    }
    }



   }

Answer 1

You may use the bsearch() library function. However, it returns an arbitrary object and not the first match. You may then iterate from the bsearch result backwards to find the first element. In principle (using char * instead of void * to have simpler code) this could look like:

    #include <stdlib.h>

    char * bsearch_first(char * key, char * arr, 
                         size_t cnt, size_t size, 
                         int(*cmp)(const void *, const void *)); 
    {
         char * result = bsearch(key,arr,cnt,size,cmp);

         if ( NULL != result ) {
             while ( arr < result && cmp(key, result - size) ) {
                 result -= size;
             }
         }
         return result;   
    }

Another approach is to implement that bsearch variant from scratch.

Then iterate all elements starting bsearch_first() until cmp() != 0 or the end if the array is reached:

    for ( item = bsearch_first(key,arr, ...);
          NULL != item 
            && item < (BYTE*)arr + sizeof arr
            && 0 == cmp(key,item);
          ++item )
    {
         do_stuff_with(item);
    }