Check if an array has a majority element
Given an array, the task is to find if the input array contains a majority element or not. An element is
Examples:
Input : arr[] = {2, 3, 9, 2, 2}
Output : Yes
A majority element 2 is present in arr[]
Input : arr[] = {1, 8, 9, 2, 5}
Output : No
A simple solution is to traverse through array. For every element, count its occurrences. If count of occurrence of any element becomes n/2, we return true.
An efficient solution is to use hashing. We count occurrences of all elements. If count becomes n/2 or more return true.
Below is the implementation of the approach.
C++
// Hashing based C++ program to find if there // is a majority element in input array. #include <bits/stdc++.h> using namespace std; // Returns true if there is a majority element // in a[] bool isMajority(int a[], int n) { // Insert all elements in a hash table unordered_map<int, int> mp; for (int i = 0; i < n; i++) mp[a[i]]++; // Check if frequency of any element is // n/2 or more. for (auto x : mp) if (x.second >= n/2) return true; return false; } // Driver code int main() { int a[] = { 2, 3, 9, 2, 2 }; int n = sizeof(a) / sizeof(a[0]); if (isMajority(a, n)) cout << "Yes"; else cout << "No"; return 0; } |
chevron_right
filter_none
Java
// Hashing based Java program // to find if there is a // majority element in input array. import java.util.*; import java.lang.*; import java.io.*; class Gfg { // Returns true if there is a // majority element in a[] static boolean isMajority(int a[], int n) { // Insert all elements // in a hash table HashMap <Integer,Integer> mp = new HashMap<Integer,Integer>(); for (int i = 0; i < n; i++) if (mp.containsKey(a[i])) mp.put(a[i], mp.get(a[i]) + 1); else mp.put(a[i] , 1); // Check if frequency of any // element is n/2 or more. for (Map.Entry<Integer, Integer> x : mp.entrySet()) if (x.getValue() >= n/2) return true; return false; } // Driver code public static void main (String[] args) { int a[] = { 2, 3, 9, 2, 2 }; int n = a.length; if (isMajority(a, n)) System.out.println("Yes"); else System.out.println("No"); } } // This code is contributed by Ansu Kumari |
chevron_right
filter_none
Python3
# Hashing based Python # program to find if # there is a majority # element in input array. # Returns true if there # is a majority element # in a[] def isMajority(a): # Insert all elements # in a hash table mp = {} for i in a: if i in mp: mp[i] += 1 else: mp[i] = 1 # Check if frequency # of any element is # n/2 or more. for x in mp: if mp[x] >= len(a)//2: return True return False # Driver code a = [ 2, 3, 9, 2, 2 ] print("Yes" if isMajority(a) else "No") #This code is contributed by Ansu Kumari |
chevron_right
filter_none
C#
// Hashing based C# program // to find if there is a // majority element in input array. using System; using System.Collections.Generic; class GFG { // Returns true if there is a // majority element in a[] static Boolean isMajority(int []a, int n) { // Insert all elements // in a hash table Dictionary<int, int> mp = new Dictionary<int, int>(); for (int i = 0; i < n; i++) { if(mp.ContainsKey(a[i])) { var val = mp[a[i]]; mp.Remove(a[i]); mp.Add(a[i], val + 1); } else { mp.Add(a[i], 1); } } // Check if frequency of any // element is n/2 or more. foreach(KeyValuePair<int, int> x in mp) if (x.Value >= n / 2) return true; return false; } // Driver code public static void Main (String[] args) { int []a = { 2, 3, 9, 2, 2 }; int n = a.Length; if (isMajority(a, n)) Console.WriteLine("Yes"); else Console.WriteLine("No"); } } // This code is contributed by PrinciRaj1992 |
chevron_right
filter_none
Output:
Yes
Recommended Posts:
- Check for Majority Element in a sorted array
- Majority element in a circular array of 0's and 1's
- Majority Element
- Majority Element | Set-2 (Hashing)
- Find the Majority Element | Set 3 (Bit Magic)
- Count majority element in a matrix
- Check for an array element that is co-prime with all others
- Check if the array has an element which is equal to XOR of remaining elements
- Check if the array has an element which is equal to sum of all the remaining elements
- Check if the last element of array is even or odd after performing a operation p times
- Check whether an array can be made strictly decreasing by modifying at most one element
- Check if the array has an element which is equal to product of remaining elements
- Check whether an array can be made strictly increasing by modifying atmost one element
- Find Array formed by adding each element of given array with largest element in new array to its left
- Form an array of distinct elements with each element as sum of an element from each array
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.
