Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Mean of range in array

  • Difficulty Level : Easy
  • Last Updated : 03 May, 2021

Given an array of n integers. You are given q queries. Write a program to print floor value of mean in range l to r for each query in a new line.

Examples : 

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

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 3
        1 2
Output : 7
         7

Naive Approach: We can run loop for each query l to r and find sum and number of elements in range. After this we can print floor of mean for each query.  



C++




// CPP program to find floor value
// of mean in range l to r
#include <bits/stdc++.h>
using namespace std;
 
// To find mean of range in l to r
int findMean(int arr[], int l, int r)
{
    // Both sum and count are
    // initialize to 0
    int sum = 0, count = 0;
 
    // To calculate sum and number
    // of elements in range l to r
    for (int i = l; i <= r; i++) {
        sum += arr[i];
        count++;
    }
 
    // Calculate floor value of mean
    int mean = floor(sum / count);
 
    // Returns mean of array
    // in range l to r
    return mean;
}
 
// Driver program to test findMean()
int main()
{
    int arr[] = { 1, 2, 3, 4, 5 };
    cout << findMean(arr, 0, 2) << endl;
    cout << findMean(arr, 1, 3) << endl;
    cout << findMean(arr, 0, 4) << endl;
    return 0;
}

Java




// Java program to find floor value
// of mean in range l to r
public class Main {
 
    // To find mean of range in l to r
    static int findMean(int arr[], int l, int r)
    {
        // Both sum and count are
        // initialize to 0
        int sum = 0, count = 0;
 
        // To calculate sum and number
        // of elements in range l to r
        for (int i = l; i <= r; i++) {
            sum += arr[i];
            count++;
        }
 
        // Calculate floor value of mean
        int mean = (int)Math.floor(sum / count);
 
        // Returns mean of array
        // in range l to r
        return mean;
    }
 
    // Driver program to test findMean()
    public static void main(String[] args)
    {
        int arr[] = { 1, 2, 3, 4, 5 };
        System.out.println(findMean(arr, 0, 2));
        System.out.println(findMean(arr, 1, 3));
        System.out.println(findMean(arr, 0, 4));
    }
}

Python3




# Python 3 program to find floor value
# of mean in range l to r
import math
 
# To find mean of range in l to r
def findMean(arr, l, r):
     
    # Both sum and count are
    # initialize to 0
    sum, count = 0, 0
     
    # To calculate sum and number
    # of elements in range l to r
    for i in range(l, r + 1):
        sum += arr[i]
        count += 1
 
    # Calculate floor value of mean
    mean = math.floor(sum / count)
 
    # Returns mean of array
    # in range l to r
    return mean
 
# Driver Code
arr = [ 1, 2, 3, 4, 5 ]
     
print(findMean(arr, 0, 2))
print(findMean(arr, 1, 3))
print(findMean(arr, 0, 4))
 
# This code is contributed
# by PrinciRaj1992

C#




//C# program to find floor value
// of mean in range l to r
using System;
 
public class GFG {
  
    // To find mean of range in l to r
    static int findMean(int []arr, int l, int r)
    {
        // Both sum and count are
        // initialize to 0
        int sum = 0, count = 0;
  
        // To calculate sum and number
        // of elements in range l to r
        for (int i = l; i <= r; i++) {
            sum += arr[i];
            count++;
        }
  
        // Calculate floor value of mean
        int mean = (int)Math.Floor((double)sum / count);
  
        // Returns mean of array
        // in range l to r
        return mean;
    }
  
    // Driver program to test findMean()
    public static void Main()
    {
        int []arr = { 1, 2, 3, 4, 5 };
        Console.WriteLine(findMean(arr, 0, 2));
        Console.WriteLine(findMean(arr, 1, 3));
        Console.WriteLine(findMean(arr, 0, 4));
    }
}
 
/*This code is contributed by PrinciRaj1992*/

PHP




<?php
// PHP program to find floor
// value of mean in range l to r
 
// To find mean of
// range in l to r
function findMean($arr, $l, $r)
{
    // Both sum and count
    // are initialize to 0
    $sum = 0;
    $count = 0;
 
    // To calculate sum and
    // number of elements in
    // range l to r
    for ($i = $l; $i <= $r; $i++)
    {
        $sum += $arr[$i];
        $count++;
    }
 
    // Calculate floor
    // value of mean
    $mean = floor($sum / $count);
 
    // Returns mean of array
    // in range l to r
    return $mean;
}
 
// Driver Code
$arr = array(1, 2, 3, 4, 5);
echo findMean($arr, 0, 2), "\n";
echo findMean($arr, 1, 3), "\n";
echo findMean($arr, 0, 4), "\n";
 
// This code is contributed by ajit
?>

Javascript




<script>
    // Javascript program to find floor value
    // of mean in range l to r
     
    // To find mean of range in l to r
    function findMean(arr, l, r)
    {
        // Both sum and count are
        // initialize to 0
        let sum = 0, count = 0;
    
        // To calculate sum and number
        // of elements in range l to r
        for (let i = l; i <= r; i++) {
            sum += arr[i];
            count++;
        }
    
        // Calculate floor value of mean
        let mean = Math.floor(sum / count);
    
        // Returns mean of array
        // in range l to r
        return mean;
    }
     
    let arr = [ 1, 2, 3, 4, 5 ];
    document.write(findMean(arr, 0, 2) + "</br>");
    document.write(findMean(arr, 1, 3) + "</br>");
    document.write(findMean(arr, 0, 4) + "</br>");
 
</script>

Output : 

2
3
3

Time Complexity: O(n)

Efficient Approach: We can find sum of numbers using numbers using prefix sum. The prefixSum[i] denotes the sum of first i elements. So sum of numbers in range l to r will be prefixSum[r] – prefixSum[l-1]. Number of elements in range l to r will be r – l + 1. So we can now print mean of range l to r in O(1). 

C++




// CPP program to find floor value
// of mean in range l to r
#include <bits/stdc++.h>
#define MAX 1000005
using namespace std;
 
int prefixSum[MAX];
 
// To calculate prefixSum of array
void calculatePrefixSum(int arr[], int n)
{
    // Calculate prefix sum of array
    prefixSum[0] = arr[0];
    for (int i = 1; i < n; i++)
        prefixSum[i] = prefixSum[i - 1] + arr[i];
}
 
// To return floor of mean
// in range l to r
int findMean(int l, int r)
{
    if (l == 0)
      return floor(prefixSum[r]/(r+1));
 
    // Sum of elements in range l to
    // r is prefixSum[r] - prefixSum[l-1]
    // Number of elements in range
    // l to r is r - l + 1
    return floor((prefixSum[r] -
          prefixSum[l - 1]) / (r - l + 1));
}
 
// Driver program to test above functions
int main()
{
    int arr[] = { 1, 2, 3, 4, 5 };
    int n = sizeof(arr) / sizeof(arr[0]);
    calculatePrefixSum(arr, n);
    cout << findMean(0, 2) << endl;
    cout << findMean(1, 3) << endl;
    cout << findMean(0, 4) << endl;
    return 0;
}

Java




// Java program to find floor value
// of mean in range l to r
public class Main {
public static final int MAX = 1000005;
    static int prefixSum[] = new int[MAX];
 
    // To calculate prefixSum of array
    static void calculatePrefixSum(int arr[], int n)
    {
        // Calculate prefix sum of array
        prefixSum[0] = arr[0];
        for (int i = 1; i < n; i++)
            prefixSum[i] = prefixSum[i - 1] + arr[i];
    }
 
    // To return floor of mean
    // in range l to r
    static int findMean(int l, int r)
    {
        if (l == 0)
           return (int)Math.floor(prefixSum[r] / (r + 1));
         
        // Sum of elements in range l to
        // r is prefixSum[r] - prefixSum[l-1]
        // Number of elements in range
        // l to r is r - l + 1
        return (int)Math.floor((prefixSum[r] -
                prefixSum[l - 1]) / (r - l + 1));
    }
 
    // Driver program to test above functions
    public static void main(String[] args)
    {
        int arr[] = { 1, 2, 3, 4, 5 };
        int n = arr.length;
        calculatePrefixSum(arr, n);
        System.out.println(findMean(1, 2));
        System.out.println(findMean(1, 3));
        System.out.println(findMean(1, 4));
    }
}

Python3




# Python3 program to find floor value
# of mean in range l to r
import math as mt
 
MAX = 1000005
prefixSum = [0 for i in range(MAX)]
 
# To calculate prefixSum of array
def calculatePrefixSum(arr, n):
 
    # Calculate prefix sum of array
    prefixSum[0] = arr[0]
 
    for i in range(1,n):
        prefixSum[i] = prefixSum[i - 1] + arr[i]
 
# To return floor of mean
# in range l to r
def findMean(l, r):
 
    if (l == 0):
        return mt.floor(prefixSum[r] / (r + 1))
 
    # Sum of elements in range l to
    # r is prefixSum[r] - prefixSum[l-1]
    # Number of elements in range
    # l to r is r - l + 1
    return (mt.floor((prefixSum[r] -
                      prefixSum[l - 1]) /
                          (r - l + 1)))
 
# Driver Code
arr = [1, 2, 3, 4, 5]
 
n = len(arr)
 
calculatePrefixSum(arr, n)
print(findMean(0, 2))
print(findMean(1, 3))
print(findMean(0, 4))
 
# This code is contributed by Mohit Kumar

C#




// C# program to find floor value
// of mean in range l to r
using System;
                     
public class GFG {
public static readonly int MAX = 1000005;
    static int []prefixSum = new int[MAX];
  
    // To calculate prefixSum of array
    static void calculatePrefixSum(int []arr, int n)
    {
        // Calculate prefix sum of array
        prefixSum[0] = arr[0];
        for (int i = 1; i < n; i++)
            prefixSum[i] = prefixSum[i - 1] + arr[i];
    }
  
    // To return floor of mean
    // in range l to r
    static int findMean(int l, int r)
    {
        if (l == 0)
           return (int)Math.Floor((double)(prefixSum[r] / (r + 1)));
          
        // Sum of elements in range l to
        // r is prefixSum[r] - prefixSum[l-1]
        // Number of elements in range
        // l to r is r - l + 1
        return (int)Math.Floor((double)(prefixSum[r] -
                prefixSum[l - 1]) / (r - l + 1));
    }
  
    // Driver program to test above functions
    public static void Main()
    {
        int []arr = { 1, 2, 3, 4, 5 };
        int n = arr.Length;
        calculatePrefixSum(arr, n);
        Console.WriteLine(findMean(1, 2));
        Console.WriteLine(findMean(1, 3));
        Console.WriteLine(findMean(1, 4));
    }
}
 
//This code is contributed by PrinciRaj1992

Javascript




<script>
 
// Javascript program to find floor value
// of mean in range l to r
let MAX = 1000005;
let prefixSum = new Array(MAX);
prefixSum.fill(0);
 
// To calculate prefixSum of array
function calculatePrefixSum(arr, n)
{
     
    // Calculate prefix sum of array
    prefixSum[0] = arr[0];
    for(let i = 1; i < n; i++)
        prefixSum[i] = prefixSum[i - 1] + arr[i];
}
 
// To return floor of mean
// in range l to r
function findMean(l, r)
{
    if (l == 0)
       return parseInt(Math.floor(prefixSum[r] /
                      (r + 1)), 10);
      
    // Sum of elements in range l to
    // r is prefixSum[r] - prefixSum[l-1]
    // Number of elements in range
    // l to r is r - l + 1
    return parseInt(Math.floor((prefixSum[r] -
                                prefixSum[l - 1]) /
                                (r - l + 1)), 10);
}
 
// Driver code
let arr = [ 1, 2, 3, 4, 5 ];
let n = arr.length;
calculatePrefixSum(arr, n);
 
document.write(findMean(1, 2) + "</br>");
document.write(findMean(1, 3) + "</br>");
document.write(findMean(1, 4) + "</br>");
 
// This code is contributed by divyeshrabadiya07
 
</script>

Output: 

2
3
3

This article is contributed by nuclode. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 




My Personal Notes arrow_drop_up
Recommended Articles
Page :