9/22/13
CAPE Computer Science Unit 2 - LiveBinder
A fast way to search a sorted array is to use abinary search. The idea is to
look at the element in the middle. If the key is equal to that, the search is
finished. If the key is less than the middle element, do a binary search on
the first half. If it's greater, do a binary search of the second half.
Pseudocode:
BinarySearch(array, size, key)
BEGIN
low = 0
high = size
while (low + 1 < high)
test = (low + high)/2
if (array[test] > key)
high = test
else
low = test
endwhile
if (array[low] = = key
return low
else
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9/22/13
CAPE Computer Science Unit 2 - LiveBinder
return -1
END
C Program:
1. #include<stdio.h>
2. #include<conio.h>
3. void main()
4. {
5. int a[10],n,i;
6. int low,high,mid,key;
7. clrscr();
8. printf(“enter the total numbers:");
9. scanf(“%d",&n);
10. printf(“enter the array elements in ascending or descending order:" );
11. for(i=0;i<n;i++)
12. scanf(“%d",&a[i]);
13.
14. low=0;
15. high=9;
16. mid=(low+high)/2;
17. printf(“\nenter the number to be searched:");
18. scanf(“%d",&key);
19. while(low<=high && a[mid]!=key)
20. {
21. if(key<a[mid])
22. high=mid-1;
23. else
24. low=mid+1;
25. mid=(low+high)/2;
26. }
27. If(a[mid]==key)
28. {
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9/22/13
CAPE Computer Science Unit 2 - LiveBinder
29. printf(“\nthe number is found at position -",mid);
30. }
31. else
32.
{
33. printf(“\nthe number is not found");
34.
}
35. getch();
36. }
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