# Maps-STL – HackerRank Solution ## Problem :

Maps are a part of the C++ STL.Maps are associative containers that store elements formed by a combination of a key value and a mapped value, following a specific order.The mainly used member functions of maps are:

Map Template :

``````std::map <key_type, data_type>
``````

Declaration :

``map<string,int>m; //Creates a map m where key_type is of type string and data_type is of type int.``

Size :

``````int length=m.size(); //Gives the size of the map.
``````

Insert :

``````m.insert(make_pair("hello",9)); //Here the pair is inserted into the map where the key is "hello" and the value associated with it is 9.
``````

Erasing an element :

``````m.erase(val); //Erases the pair from the map where the key_type is val.
``````

Finding an element :

``````map<string,int>::iterator itr=m.find(val); //Gives the iterator to the element val if it is found otherwise returns m.end() .
Ex: map<string,int>::iterator itr=m.find("Maps"); //If Maps is not present as the key value then itr==m.end().``````

Accessing the value stored in the key :

``````To get the value stored of the key "MAPS" we can do m["MAPS"] or we can get the iterator using the find function and then by itr->second we can access the value.
``````

You are appointed as the assistant to a teacher in a school and she is correcting the answer sheets of the students.Each student can have multiple answer sheets.So the teacher has `Q` queries:

1. `X Y`  :Add the marks `Y` to the student whose name is `X`.
2. `X` : Erase the marks of the students whose name is `X`.
3. `X` : Print the marks of the students whose name is `X`. (If `X` didn’t get any marks print `0`.)

### Sample Input :

``````7
1 Jesse 20
1 Jess 12
1 Jess 18
3 Jess
3 Jesse
2 Jess
3 Jess``````

### Sample Output :

``````30
20
0``````

## Solution :

``````#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <map>
#include <algorithm>
using namespace std;

int main() {
int n, a, b;
string name;
cin >> n;
map<string, int>m;
for(int i = 0; i < n; i++) {
cin >> a >> name;
if(a == 1) {
cin >> b;
m[name] += b;
} else if (a == 2) {
m.erase(name);
} else if (a == 3) {
map<string, int>::iterator itr = m.find(name);
cout << (itr == m.end() ? 0 : itr->second) << endl;
}
}
return 0;
}
``````

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