This document discusses two algorithms for searching arrays: linear search and binary search. Linear search simply checks each element of the array sequentially to find a target value, while binary search relies on the array being sorted and checks elements in a divide-and-conquer manner by repeatedly dividing the search space in half. The document provides pseudocode to illustrate how binary search works and compares the advantages of each approach.

1. Searching in Arrays
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Instructor
Dhiviya Rose J , AP-Sr. Scale | SoCSE

2. INFO 106 – Computer Programming
Searching Arrays: Linear Search and
Binary Search
• Search an array for a key value
• Linear search
▫ Simple
▫ Compare each element of array with key value
▫ Useful for small and unsorted arrays
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3. INFO 106 – Computer Programming
Linear Search
• Step through array of records, one at a time.
• Look for record with matching key.
• Search stops when
▫ record with matching key is found
▫ or when search has examined all records without
success.

4. INFO 106 – Computer Programming
How Linear Search works
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Case 1: Target
found

6. 6
Case 1: Target NOT
found

7. INFO 106 – Computer Programming
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Program
#include<stdio.h>
void main()
{
int a[10],i,target;
printf("Enter array value n");
for(i=0;i<n;i++)
scanf("%d",&a[i]);
printf("Which value to be search ->");
scanf("%d",&target);
/* Linear Search logic */
for(i=0;i<n;i++)
if(target==a[i])
{
printf(“Value found at %d”,i);
}
}

8. INFO 106 – Computer Programming
Advantages of Linear Search
• Don't have to sort the data we search.
• Works well if only search operation is minimum
• Not optimal in case of large amount of data
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9. INFO 106 – Computer Programming
Binary Search
• Assume that we are give an array of records that
is sorted. For instance:
▫ an array of records with integer keys sorted from
smallest to largest (e.g., ID numbers), or
▫ an array of records with string keys sorted in
alphabetical order (e.g., names).

10. Binary Search
[ 0 ] [ 1 ]
Example: sorted array of integer keys. Target=7.
3 6 7 11 32 33 53
[ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ]

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12. INFO 106 – Computer Programming
Binary Search Pseudocode
…
if(size == 0)
found = false;
else {
middle = index of approximate midpoint of array segment;
if(target == a[middle])
target has been found!
else if(target < a[middle])
search for target in area before midpoint;
else
search for target in area after midpoint;
}
…

13. INFO 106 – Computer Programming
Program
int result=-1;
int low=0;
int high=length-1;
int mid;
while( result==-1 && low<=high )
{ mid= low + ((high - low) / 2);
if( list[mid] == target )
result = mid;
else if( list[mid] < target)
low = mid + 1;
else
high = mid - 1;
}
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14. INFO 106 – Computer Programming
Other Searching Algorithms
• Interpolation Search
• Indexed Searching
• Binary Search Trees
• Hash Table Searching
• Grover's Algorithm
• Best-first
• A*
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