Maps-STL C++ HackerRank Solution
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:
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Map Template:
std::map <key_type, data_type>
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Declaration:
map<string,int>m; //Creates a map m where key_type is of type string and data_type is of type int.
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Size:
int length=m.size(); //Gives the size of the map.
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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.
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Erasing an element:
m.erase(val); //Erases the pair from the map where the key_type is val.
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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().
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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.
ou 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 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
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1 <= Q <= 10^5
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1 <= type <= 3
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1 <= |X| <= 6
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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
#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 */
int q;
cin >> q;
map<string, int> mp;
for (int i = 0; i < q; i++) {
int type;
cin >> type;
if (type == 1) {
string name;
int marks;
cin >> name >> marks;
mp[name] += marks;
} else if (type == 2) {
string name;
cin >> name;
mp.erase(name);
} else if (type == 3) {
string name;
cin >> name;
cout << mp[name] << endl;
}
}
return 0;
}
