Hackerrank Maps-STL Solution
- Published
- Updated
- Reading time
- 5 min read
- Length
- 686 words
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 queries:
:Add the marks to the student whose name is .
: Erase the marks of the students whose name is .
: Print the marks of the students whose name is . (If didn't get any marks print .)
Input Format
The first line of the input contains where is the number of queries. The next lines contain query each.The first integer, of each query is the type of the query.If query is of type , it consists of one string and an integer and where is the name of the student and is the marks of the student.If query is of type or ,it consists of a single string where is the name of the student.
Constraints
Output Format
For queries of type 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 JessSample Output
30
20
0Solution in cpp#
Approach 1.
#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;
for(int i=0;i<n;i++){
int n1,y;
string z;
cin >> n1 ;
if(n1 == 1){
cin >> z >> y;
if(!m.empty())
m[z] +=y;
else
m.insert(make_pair(z,y));
}
else if(n1==2){
cin >> z;
m.erase(z);
}
else{
cin >> z;
cout << m[z] << endl;
}
}
/* Enter your code here. Read input from STDIN. Print output to STDOUT */
return 0;
}Approach 2.
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <map>
#include <algorithm>
using namespace std;
int main() {
map <string,int> m;
map <string,int>::iterator iter;
int n, qtype, val;
string key;
cin >> n;
for (int i = 0; i < n; i++) {
cin >> qtype >> key;
if (qtype == 1) {
cin >> val;
iter = m.find(key);
if (iter == m.end())
m.insert(make_pair(key,val));
else
m[key] += val;
} else if (qtype == 2) {
m.erase(key);
} else if (qtype == 3) {
cout << m[key] << "\n";
}
}
return 0;
}Approach 3.
#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 */
map<string,int>m;
int n;
cin>>n;
while(n-->0){
int cmd;
string name;
cin>>cmd>>name;
if(cmd==1){
std::pair<std::map<string,int>::iterator,bool> ret;
int score;
cin>>score;
ret = m.insert(std::pair<string,int>(name,score));
if(ret.second == false){
ret.first->second = ret.first->second + score;
}
}
if(cmd==2){
m.erase(name);
}
if(cmd==3){
cout<<m[name]<<endl;
}
}
return 0;
}
