Java Program for Range Queries for Frequencies of array elements

Java Program for Range Queries for Frequencies of array elements

Last Updated : 06 Jan, 2022

Given an array of n non-negative integers. The task is to find frequency of a particular element in the arbitrary range of array[]. The range is given as positions (not 0 based indexes) in array. There can be multiple queries of given type.
Examples:

Input  : arr[] = {2, 8, 6, 9, 8, 6, 8, 2, 11};
         left = 2, right = 8, element = 8
         left = 2, right = 5, element = 6      
Output : 3
         1
The element 8 appears 3 times in arr[left-1..right-1]
The element 6 appears 1 time in arr[left-1..right-1]

Naive approach: is to traverse from left to right and update count variable whenever we find the element.
Below is the code of Naive approach:-

Java

// JAVA Code to find total count of an element
// in a range

class GFG {
    
    // Returns count of element in arr[left-1..right-1]
    public static int findFrequency(int arr[], int n, 
                                int left, int right,
                                      int element)
    {
        int count = 0;
        for (int i = left - 1; i < right; ++i)
            if (arr[i] == element)
                ++count;
        return count;
    }
    
    /* Driver program to test above function */
    public static void main(String[] args) 
    {
        int arr[] = {2, 8, 6, 9, 8, 6, 8, 2, 11};
        int n = arr.length;
     
        // Print frequency of 2 from position 1 to 6
        System.out.println("Frequency of 2 from 1 to 6 = " +
             findFrequency(arr, n, 1, 6, 2));
     
        // Print frequency of 8 from position 4 to 9
        System.out.println("Frequency of 8 from 4 to 9 = " +
             findFrequency(arr, n, 4, 9, 8));
        
    }
  } 
// This code is contributed by Arnav Kr. Mandal.

Output:

 Frequency of 2 from 1 to 6 = 1
 Frequency of 8 from 4 to 9 = 2

Time complexity of this approach is O(right - left + 1) or O(n)
Auxiliary space: O(1) Please refer complete article on Range Queries for Frequencies of array elements for more details!

Java Program for Range Queries for Frequencies of array elements

kartik

Improve

Article Tags :

Practice Tags :

Similar Reads

Java Program for Mean of range in array

Given an array of n integers. You are given q queries. Write a program to print the floor value of mean in range l to r for each query in a new line. Examples : Input : arr[] = {1, 2, 3, 4, 5} q = 3 0 2 1 3 0 4 Output : 2 3 3 Here for 0 to 2 (1 + 2 + 3) / 3 = 2 Input : arr[] = {6, 7, 8, 10} q = 2 0

Java Program for Range LCM Queries

Given an array of integers, evaluate queries of the form LCM(l, r). There might be many queries, hence evaluate the queries efficiently.Â Â LCM (l, r) denotes the LCM of array elements that lie between the index l and r (inclusive of both indices) Mathematically, LCM(l, r) = LCM(arr[l], arr[l+1] , ..

Java Program to Find the GCDs of given index ranges in an array

Write a Java program for a given array a[0 . . . n-1], the task is to find the GCD from index qs (query start) to qe (query end) where 0 <= qs <= qe <= n-1. Example: Input: arr[] = {2, 3, 60, 90, 50};Index Ranges: {1, 3}, {2, 4}, {0, 2}Output: GCDs of given ranges are 3, 10, 1Explanation: E

How to Perform Range Queries on a PriorityQueue in Java?

Based on a priority heap, a Java PriorityQueue represents an unlimited priority queue. PriorityQueue does not directly handle range queries, but it does provide quick access to the element with the greatest priority. On the other hand, range queries may be executed by taking pieces from the Priority

Java Program to Print All the Repeated Numbers with Frequency in an Array

The frequency of an element in an array is the count of the occurrence of that particular element in the whole array. Given an array that may contain duplicates, print all repeated/duplicate elements and their frequencies. Below is the discussion of this program by two approaches: Using a counter ar

Java Program to Count of Array elements greater than all elements on its left and at least K elements on its right

Given an array A[ ] consisting of N distinct integers, the task is to find the number of elements which are strictly greater than all the elements preceding it and strictly greater than at least K elements on its right. Examples: Input: A[] = {2, 5, 1, 7, 3, 4, 0}, K = 3 Output: 2 Explanation: The o

Count occurrences of elements of list in Java

Suppose we have an elements in ArrayList, we can count the occurrences of elements present in a number of ways. HashMap This data structure uses hash function to map similar values, known as keys to their associated values. Map values can be retrieved using key as it contains key-value pairs. Java /

Find Occurrence of Number More Than N/2 Times in a Sorted Array in Java

Given a Sorted Array of n integers, and an Integer X, the task is to find whether the given Integer X appears more than n/2 times in the array or not. Input: arr[] = {1,1,2,3,3,3,3,3,3,3,3,3,4,5,6,6,7}, x=3 Output: 3 occurs 9 times which is more than 8 times Input: arr[] = {1,1,2,3,3,3,3,3,3,3,3,3,4

Javascript Program for Range Queries for Frequencies of array elements

Given an array of n non-negative integers. The task is to find frequency of a particular element in the arbitrary range of array[]. The range is given as positions (not 0 based indexes) in array. There can be multiple queries of given type. Examples: Input : arr[] = {2, 8, 6, 9, 8, 6, 8, 2, 11}; lef

C++ Program for Range Queries for Frequencies of array elements

Given an array of n non-negative integers. The task is to find frequency of a particular element in the arbitrary range of array[]. The range is given as positions (not 0 based indexes) in array. There can be multiple queries of given type.Â Examples:Â Â Input : arr[] = {2, 8, 6, 9, 8, 6, 8, 2, 11}; l