Reputation: 5
I coded a simple binary search to print out the position of what was searched. It correctly recognizes when a searched element isn't in the array and prints out "error". However, when a searched element is actually in the array, the value is printed, rather than the position. Could you please let me know what i'm missing? Thanks in advance
#include <stdio.h>
#include <stdlib.h>
int binarysearch(int array[], int low, int max, int search);
int main(void) {
int array[10]={10,11,12,13,14,15,16,17,18,19};
int count,search;
count=sizeof(array)/sizeof(array[0]);
printf("Enter the number you would like to search\n");
scanf("%d",&search);
int result=binarysearch(array,0,count,search);
if (result>0){
printf("Element in position %d",result);
}
else{
printf("Error");
}
}
int binarysearch(int array[], int low, int max, int search){
if(low<=max){
int middle=(low+max)/2;
if(search>array[middle]){
low=middle+1;
return binarysearch(array,low,max,search);
}
else if(search<array[middle]){
max=middle-1;
return binarysearch(array,low,max,search);
}
else {
return search;
}
}
else
return -1;
}
Upvotes: 0
Views: 86
Reputation: 30936
Apart from the return middle;
(in place of return search
) change you should also change the
if (result>=0){
^^^^
printf("Element in position %d",result);
}
Otherwise you will always miss the 0-th element even if found. (By miss I mean the result won't be printed). Binary search will work as intended.
One another thing to notice is while calculating mid
to avoid overflow use this
int middle = low + ((max - low) / 2);
Finally, the use of recursion is purely wasteful.
int binarysearch(int array[], int low, int max, int search) {
while (low <= max) {
int middle = low + ((max - low) / 2);
if (search > array[middle]) {
low = middle + 1;
}
else if (search < array[middle]) {
max = middle - 1;
}
else {
return middle;
}
}
return -1;
}
Upvotes: 2