Given a queue of integers, the task is to write a program that efficiently finds the largest element in that queue. Return -1 if the queue is empty.
Examples:
Input: Queue = {15, 27, 18}
Output: 27
Explanation: Among 15(front), 27 and 18(back), 27 is the largest.Input: Queue = {12, 25, 29, 16, 32}
Output: 32
Explanation: Among 12(front), 25, 29, 16 and 32(back), 32 is the largest.
Naive Approach: The basic way to solve the problem is as follows:
The naive approach to finding the largest element in a queue is to just pop each element from the queue and store them in an array/vector. Then find largest element in that array.
Time Complexity: O(N), where N is the number of elements in the queue.
Auxiliary Space: O(N)
Efficient Approach: The efficient approach is to find the maximum/largest element of the queue during popping elements from the queue as follows:
- Store the current front element in the temp variable and then pop that element.
- Now, compare that temp with maxx and store the maximum value into maxx.
Below is the implementation of the above approach:
C++
// C++ program to find the largest// element present in the queue#include <bits/stdc++.h>using namespace std;// Function which return// largest element of the queueint maxElement(queue<int> q){ // If queue is empty return -1 if (q.empty()) return -1; // To store the largest element int maxx = INT_MIN; // Loop which iterate until // queue becomes empty while (!q.empty()) { // Store the current front element int temp = q.front(); // pop current front element q.pop(); // Store maximum value between // temp and maxx maxx = max(maxx, temp); } // Return largest value return maxx;}// Driver Codeint main(){ queue<int> q; // Pushing elements into queue q.push(15); q.push(27); q.push(18); // Call function and store // return value into maxx int maxx = maxElement(q); // print the largest element cout << maxx << endl; return 0;}// This code is contributed by Susobhan Akhuli |
Java
// Java program to find the largest// element present in the queueimport java.util.LinkedList;import java.util.Queue;public class Main { // Function which returns the //largest element of the queue static int maxElement(Queue<Integer> q) { // If the queue is empty, return -1 if (q.isEmpty()) return -1; // To store the largest element int maxx = Integer.MIN_VALUE; // Loop which iterates until //the queue becomes empty while (!q.isEmpty()) { // Store the current front element int temp = q.peek(); // Remove the current front element q.poll(); // Store the maximum value //between temp and maxx maxx = Math.max(maxx, temp); } // Return the largest value return maxx; } // Driver Code public static void main(String[] args) { Queue<Integer> q = new LinkedList<>(); // Pushing elements into the queue q.add(15); q.add(27); q.add(18); // Call the function and store the // return value into maxx int maxx = maxElement(q); // Print the largest element System.out.println(maxx); }}// This code is contributed by Susobhan Akhuli |
Python3
# Python program to find the# largest element present# in the queuefrom queue import Queue# Function which return largest element# of the queuedef maxElement(q: Queue) -> int: # If queue is empty return -1 if q.empty(): return -1 # To store the largest element maxx = float('-inf') # Loop which iterate until # queue becomes empty while not q.empty(): # Store the current front element temp = q.get() # pop current front element # Store maximum value # between temp and maxx maxx = max(maxx, temp) # Return largest value return maxx# Driver Codeif __name__ == '__main__': q = Queue() # Pushing elements into queue q.put(15) q.put(27) q.put(18) # Call function and store # return value into maxx maxx = maxElement(q) # print the largest element print(maxx)# This code is contributed by Susobhan Akhuli |
C#
// C# program to find the largest// element present in the queueusing System;using System.Collections.Generic;class GFG { static int MaxElement(Queue<int> q) { // If queue is empty return -1 if (q.Count == 0) return -1; // To store the largest element int max = int.MinValue; // Loop which iterate until queue becomes empty while (q.Count > 0) { // Store the current front element int temp = q.Dequeue(); // Store maximum value between temp and max max = Math.Max(max, temp); } // Return largest value return max; } static void Main() { Queue<int> q = new Queue<int>(); // Pushing elements into queue q.Enqueue(15); q.Enqueue(27); q.Enqueue(18); // Call function and store return value into max int max = MaxElement(q); // Print the largest element Console.WriteLine(max); // Keep the console window open Console.ReadLine(); }}// This code is contributed by Susobhan Akhuli |
Javascript
// Javascript program to find the largest// element present in the queue// Function which returns the largest element of the queuefunction maxElement(q) { // If queue is empty return -1 if (q.length === 0) { return -1; } // To store the largest element let maxx = Number.MIN_SAFE_INTEGER; // Loop which iterates until queue becomes empty while (q.length !== 0) { // Store the current front element let temp = q[0]; // Remove current front element q.shift(); // Store maximum value between temp and maxx maxx = Math.max(maxx, temp); } // Return largest value return maxx;}// Driver Codelet q = [];// Pushing elements into queueq.push(15);q.push(27);q.push(18);// Call function and store return value into maxxlet maxx = maxElement(q);// Print the largest elementconsole.log(maxx);// This code is contributed by Susobhan Akhuli |
Output
27
Time Complexity: O(N), where N is the number of elements in the queue.
Auxiliary Space: O(1)
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