my java solution, all tests pass.

public static int sockMerchant(int n, List ar) { // Write your code here Map map = new HashMap<>(); for(int i=0; i< ar.size(); i++) { if(!map.containsKey(ar.get(i))) map.put(ar.get(i), 1); else { map.put(ar.get(i), map.get(ar.get(i))+1); } } int numPairs=0; Iterator i = map.values().iterator(); while(i.hasNext()) { numPairs = numPairs + (int)i.next()/2; } return numPairs; }

Here is my c++ solution , you can find the video explanation here : https://youtu.be/HPIhFXx_DVM

int sockMerchant(int n, vector<int> ar) {
    map<int, int>mp;
    int result = 0;
    for(int i = 0; i < ar.size(); i++){
        if(mp[ar[i]]){
            result ++;
            mp.erase(ar[i]);
            continue;
        }
        mp[ar[i]]++;
    }
    return result;
}

def sockMerchant(n, ar): pair = 0

set1 = list(set(ar))
for i in set1:
    if ar.count(i) % 2 == 0:
        pair = pair + ar.count(i)/2
    elif ar.count(i)%2 == 1:
        pair = pair+((ar.count(i)-1)/2)
return int(pair)

Python 3

def sockMerchant(n, ar):
    r = 0
    
    for i in set(ar):
        r += ar.count(i) // 2
    return r