Count All Occurrences of an Element in an Array

“Count All Occurrences of an Element in an Array” is a basic problem of array data structure. Here, we are given an array of size ‘n’ and an element ‘x’. Our task is to write a program to count all occurrences of an element in an array.

Example (Count All Occurrences of an Element in an Array):

INPUT:
Enter the size of an array: 10
Enter Array Elements:
12 13 11 12 45 67 13 11 12 43
Enter an element to count: 12
OUTPUT:
The number of occurrences of 12 are: 3

The steps required to count all occurrences of an element in an array are as follows:

1. Scan the size of array and elements of the array from user.
2. Scan the key element whose occurrences needed to be count from the array.
3. Set Count = 0.
4. Iterate over each element and check whether it is equal to key element or not. If element is key element, increment count as: Count = Count + 1.
5. Print the result as Count.

C++ Program to count all occurrences of an element in an array is as follows:

/* Program to count all occurrences of an element in an array */  
#include<bits/stdc++.h>  
using namespace std;  
int main()  
{  
    /* Scan size of array */  
    int n;  
    cout<<"Enter the size of an array: ";  
    cin>>n;  
      
    /* Scan Array Elements */  
    int arr[n];  
    cout<<"\nEnter array elements:\n";  
    for(int i = 0; i < n; i++)  
    {  
        cin>>arr[i];  
    }  
      
    /* Scan key element */  
    int key;  
    cout<<"\nEnter key element: ";  
    cin>>key;  
      
    int count = 0;  
      
    /* Count occurence of key element in an array */  
    for(int i = 0; i < n; i++)  
    {  
        if(arr[i] == key)  
        count = count + 1;  
    }  
      
    /*Printing the result */  
    cout<<"\nThe number of occurences of "<<key<<" are: "<<count;  
}  

OUTPUT:
Enter the size of an array: 
Enter array elements:
1 3 2 3 5
Enter key element: 
The number of occurences of 3 are: 2
Time Complexity:
O(n), where ‘n’ is the size of an element

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