Count the Number of Occurrences of a Number in an Array
This lesson will teach you how to find the number of occurrences of a particular number in an array using recursion.
Total Occurrences of a Number
The number of occurrences of a number means the frequency a number n appears in the array.
The following illustration explains the concept:
Implementing the Code
The following code explains how to find the frequency of a number in an array using recursion.
Experiment with the code by changing the values of array
and num
to see how it works!
import java.io.*;class ArrayClass {private static int noOfOccurrences(int[] a, int key, int currentIndex) {if (a.length == currentIndex) {return 0;}else if (a[currentIndex] == key) {return 1 + noOfOccurrences(a, key, currentIndex+1);}else {return noOfOccurrences(a, key, currentIndex+1);}}public static void main(String[] args) {System.out.print("{");int[] array = {2,3,4,1,7,8,3};for (int i = 0; i < array.length; i++) {System.out.print(array[i] + " ");}System.out.println("}");int key = 3;int output = noOfOccurrences(array, key, 0);System.out.println("Number of occurrences of " + key + ": " + output);}}
Understanding the Code
The code snippet above can be broken down into two parts. The recursive method and ...