Please help me to know what is happening in this code

string kthDistinct(vector<string>& arr, int k) {
    unordered_map<string, int> m;
    for (auto &s : arr)
        ++m[s];
//Frome here
    for (auto &s : arr)
        if (m[s] == 1 && --k == 0)
            return s;
    return "";
//to here 
}

Especially in this part
for (auto &s : arr)
if (m[s] == 1 && –k == 0)
return s;

>Solution :

That block of code is a bit on the dense side. If we rewrite the same logic in a more verbose manner, we get:

for (auto &s : arr) {
  if( m[s] == 1 ) {
    k -= 1;
    if( k == 0 ) {
      return s;
    } 
  }

Since m contains the number of time a string appears within arr, we can interpret this as:

"Return the kth string of arr that appears only once within arr."