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Most frequent element in an array in C++
We are given a array and we need to find the most frequent element from it. Let's see an example.
Input
arr = [1, 2, 3, 3, 2, 2, 1, 1, 2, 3, 4]
Output
2
In the above array, 2 occurs 4 times which is most frequent than any other in the array.
Algorithm - 1
Initialise the array.
Initialise a map to store the frequency of each element.
Count the frequency of each element and store it in the map.
Iterate over the map and find the element with most frequency.
- Return the element.
Algorithm - 2
- Initialise the array.
- Sort the given array.
- Maintain the variables for max count, result and current element count.
- Find the max count element by iterating over the array.
- Same elements resides side by side.
- Return the result.
Implementation
Following is the implementation of the above algorithm in C++
#include <bits/stdc++.h>
using namespace std;
int getMostFrequentNumber(int arr[], int n) {
unordered_map<int, int> elements;
for (int i = 0; i < n; i++) {
elements[arr[i]]++;
}
int maxCount = 0, res = -1;
for (auto i : elements) {
if (maxCount < i.second) {
res = i.first;
maxCount = i.second;
}
}
return res;
}
int main() {
int arr[] = { 1, 2, 3, 3, 2, 2, 1, 1, 2, 3, 4 };
int n = 11;
cout << getMostFrequentNumber(arr, n) << endl;
return 0;
}Output
If you run the above code, then you will get the following result.
2
Updated on: 25-Oct-2021
4K+ Views
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