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Ace the AP Computer Science Exam for High Schoolers

Searching Algorithms

Explore the fundamental searching algorithms used in computer science, including sequential and binary search. Understand how to implement these algorithms in Java to efficiently locate values in arrays. This lesson helps you grasp core concepts and coding techniques crucial for acing your AP Computer Science exam.

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Overview

One of the main advantages a computer offers is storing large amounts of data. Computers can find things quicker than humans. This capability is called searching. There are two main types of searching techniques:

  • Sequential search
  • Binary search

Sequential search

Going through all items, one by one, until we find the desired item is called a sequential search. It is also known as a linear search.

For example, if we have the following array, and we need to find 55, we’ll check all the elements one by one.

It’s very easy to code a sequential search in Java. Let’s begin.

Java
class SequentialSearch 
{
    public static int search(int[] array, int value)
    {
        for(int i = 0; i < array.length; i++)   // Traversing through array
        {
          if(value == array[i])                 // If element found
              return i;
        }
        return -1;                              // Element not found
    }   
    
    public static void main( String args[] ) {
        int[] array = {1, -2, 71, -4, 40, 32};
        // Searching different values
        System.out.println(search(array, -4));
        System.out.println(search(array, 0));
    }
}

Look at line 3. We create the header of the search() function. It takes the array and a value that is to be searched. As a result, it will return the index of the value. If the value isn’t found, it returns −1-1 ...