[STL] day 1~2 Problem Set

Q#1

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

void print(int& t){    //for_each fnc: parameter accept elements T
    cout << t << " ";
}

int main() {
    vector<int> v;
    int num, toPut;
    cin >> num;
    ; i<num; i++) {
        cin >> toPut;
        v.push_back(toPut);
    }
    sort(v.begin(), v.end()); 

    for_each(v.begin(), v.end(), print);     //calling fnc in for_each 

    ;
}

Q#2

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

void print(int& i){
    cout << i << " ";
}

int main() {
    vector<int> v;
    int size, num;
    cin >> size;
    ; i<size; i++){
        cin >> num;
        v.push_back(num);
    }

    int toErase1, toErase2;
    cin >> toErase1;
    v.erase(v.begin()+toErase1-);
    cin >> toErase1 >>toErase2;
    toErase1--; toErase2--;
    v.erase(v.begin()+toErase1, v.begin()+toErase2);　　//last one exclusive

    cout << v.size() <<endl;
    for_each(v.begin(), v.end(), print);

    ;
}

Q#3: time-out exception

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

int main() {
    vector<int> v;
    int size, num, time, target;
    cin >> size; 

    ; i<size; i++){
        cin >> num;
        v.push_back(num);
    }

    cin >> time;
    ; t<time; t++){  //start testing each case
        cin >> target;
        ; 

        for(; i<v.size(); i++){
           if(v[i]!=target) continue;
            <<endl; break;
        }  

        if(i == v.size()){
            ; j<v.size(); j++){
                 <<endl; break;} 　　　//should not forget the {} in one-line code
            }
        }
    }
}

Q#4

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

int main() {
    set<int> s;
    int num, enquiryType, item; 

    cin >> num;
    while(num){
        cin>>enquiryType;
        cin >> item;
        switch(enquiryType){
            : s.insert(item); break;
            : s.erase(item); break;
            : {
                set<int>::const_iterator p = s.find(item);
                if(p!=s.end()) cout << "Yes" <<endl; 　　//cannot use if(p!=NULL); Cz even p == v.end(), v.end()!=NULL;
                else cout << "No" <<endl;
                break;
            }
        }
    num--;
    }

}

Q#5

#include <cstdio>
#include <iostream>
#include <map>
#include <algorithm>
#include <string>
using namespace std;

int main() {
    map<string, int> students;
    int num, marks, choice;
    string name;
    cin >> num;
    while(num){
        cin >> choice >> name;
        switch(choice){
            : {
                cin >> marks;
                map<string, int>::iterator p = students.find(name);　　　　//stl algorithm needed be called by a STL CONTAINER! NOT STANDALONE!
                if(p!=students.end()){　　　　//rmb: after 'find()' algorithm, found if p!=container.end();
                     && marks!= && marks!=) students[name] += marks; 　　//container name with key represents the value it contains!
                    break;
                }

                 && marks!= && marks!=) students.insert(pair<string, int>(name, marks));
                ));
                break;
            }

            : {
                students.erase(name); break;
            }
            :{
                cout << students[name] <<endl;
            }
        }

        num--;
    }
}