Sock Merchant

John works at a clothing store. He has a large pile of socks that he must pair by color for sale. Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

For example, there are  socks with colors . There is one pair of color  and one of color . There are three odd socks left, one of each color. The number of pairs is .

Function Description

Complete the sockMerchant function in the editor below. It must return an integer representing the number of matching pairs of socks that are available.

sockMerchant has the following parameter(s):

• n: the number of socks in the pile
• ar: the colors of each sock

Input Format

The first line contains an integer , the number of socks represented in .
The second line contains  space-separated integers describing the colors  of the socks in the pile.

Constraints

•  where 

Output Format

Return the total number of matching pairs of socks that John can sell.

Sample Input

9

10 20 20 10 10 30 50 10 20

Sample Output

3

Solution:

//code by anewbieprogrammer

#include<iostream>

using namespace std;

void merge(int arr[], int s, int e, int mid){

    int temp[100];

    int i = s;

    int k = s;

    int j = mid + 1;    

    while(i <= mid && j <= e){

        if(arr[i] <= arr[j])

            temp[k++] = arr[i++];

        else

            temp[k++] = arr[j++];

    }        

    while(i <= mid){

        temp[k++] = arr[i++];

    }

    while(j <= e){

        temp[k++] = arr[j++];

    }    

    for(int i = s; i <= e; i++){

        arr[i] = temp[i];

    }        

}

void sort(int arr[], int s, int e){

    if(s >= e){

        return;

    }

    int mid = (s + e) / 2;

    sort(arr, s, mid);

    sort(arr, mid+1, e);    

    merge(arr, s, e, mid);    

}

int sockMerchant(int arr[], int total){

    int count=1, sum = 0;

    int pair[100];

    int c = 0;

    sort(arr, 0, total-1);

    int temp = arr[0];

    for(int it = 1; it < total; it++){

        if(temp == arr[it])++count;

        else{

            pair[c++] = count;

            temp = arr[it];

            count = 1;

        }

    }

    pair[c++] = count;

    for(int it = 0; it < c; it++){

        int r = pair[it] / 2;

        sum += r;

    }

    return sum;  

}

int main(){

    int total;

    cin>>total;

    int arr[total];

    for(int it = 0; it < total; it++){

        cin>>arr[it];

    }    

    cout<<sockMerchant(arr, total);

}