Maps-STL in C++ – Solution in Hacker Rank - hackerranksolutions8

 

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.

To know more about maps click Here.
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 student whose name is X.
3. X : print the marks of the student whose name is X. (if X didn’t get any marks print 0. )

---

Input Format :

The first line of the input contains Q where Q is the number of queries. The next Q lines contain 1 query each.The first integer, type of each query is the type of the query. If query is of type 1, it consists of one string and an integer X and Y where X is the name of the student and Y is the marks of the student. If query is of type 2 or 3, it consists of a single string X where X is the name of the student.

Constraints :

• 1 <= Q <= 10^5
• 1 <= type <= 3
• 1 <= |X| <= 6
• 1 <= Y <= 10^3

Output Format :

For queries of type 3 print the marks of the given student.

---

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 :

//Maps-STL in C++ - Hacker Rank Solution
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <map>
#include <algorithm>
using namespace std;


int main() 
{
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    /*Maps-STL in C++ - Hacker Rank Solution START */  
    map <string,int> m;
    int N = 0;
    cin >> N;
    for (int i = 0; i < N; i++)
    {
        int q = 0;
        cin>>q;
        string x;
        if (q == 1)
        {
            int y = 0;
            cin>>x;
            cin>>y;
            m[x] += y;
        }
        else if (q == 2)
        {
            cin>>x;
            m.erase(x);
        }
        else
        {
            cin>>x;
            map<string,int>::iterator itr=m.find(x);
            if (itr != m.end())
                cout<<m[x]<<endl;
            else
                cout<<0<<endl;
        }
    }
    /* Maps-STL in C++ - Hacker Rank Solution END */
    return 0;
}