Maps-STL C++
Problem Statement :
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 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.)
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 is X 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.
Solution :
Solution in C :
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <map>
#include <algorithm>
using namespace std;
int main() {
int n;
cin >> n;
map<string, int> m;
while (n--) {
int t;
cin >> t;
string s;
cin >> s;
if (t == 1) {
int a;
cin >> a;
m[s] += a;
} else if (t == 2) {
m[s] = 0;
} else {
cout << m[s] << "\n";
}
}
return 0;
}
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