Thread: Need help with binary search

Hello all, I am currently writing a program that deals with binary searching.To give you some background on the program, a file is opened, loaded into an array.From there, the string the user enters is passed to a function that searches to see if that word exists within the file. Now, I can't seem to get it to work. It's returning false everytime the function executes.here is the code I have

Code:

int first=0;
int last =0;
word findword;
last=dictionary.size-1;
int middle=0;
int position=-1;
 

findword.found=false;
 
  while(findword.found==false && first<=last)
 {
  middle=(first+last)/2;
  if (strcmp(s,dictionary.words[middle].letters)==0)
  
  
    {
     findword.found=true;
     position=middle;
     return true;
    }
   else if (dictionary.words[middle].letters>s)
   {
     last=middle-1;
   }
   else
   first=middle+1;
   }
   return false;
  }

Your function lost me. Try it like this:

Code:

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

int binarySearch(char words[6][30], char target[6]);

int main(void) {  
   int i;
   char words[6][30] = {
   {"Alfa"},{"Bravo"},{"Charlie"},{"Delta"},{"Echo"},{"Foxtrot"}};
   char target[30];

   printf("Enter the word you are searching for: ");
   fflush(stdout);
   scanf("%s",target);
   
   i=binarySearch(words,target);

   if(i>-1)  //zero is a legitimate array index
      printf("Found it, index %d in the array\n",i);
   else
      printf("Target word: %s was not found in the list\n",target);
   
  

   return 0;
}
int binarySearch(char words[6][30], char target[30]) {
   int i, lo=0,hi=5,mid;
   
   while(lo<=hi) {
      mid = (lo + hi)/2;
      i=strcmp(words[mid],target);
              //helpful for debugging:
              //printf("i:%d  mid:%d  words[mid]: %s\n",i,mid,words[mid]); getchar();
      if(i>0) {
         hi=mid-1;
      }else if(i<0) {
         lo=mid+1;
      }else
         return mid; //target was found, this is it's index
   }
   return -1; //target was not found

}