Skip to content

Latest commit

 

History

History

C++ STL

Folders and files

NameName
Last commit message
Last commit date

parent directory

..
README.rst
README.rst
 
 

README.rst

STL

vector

#include<bits/stdc++.h>
using namespace std;
int main()
{int arr[] = {1, 3, 4, 7, 4, 2, 7, 9, 5, 6};
    vector<int> v;
    v.assign(arr, arr+10);
    for(auto it : v)
        cout << it << " ";
}
#include<bits/stdc++.h>
using namespace std;
int main()
{
    vector <int> A = {2, 4, 7, 5 , 1};
    sort(A.begin(), A.end());   //O(NlogN) sorting

    bool present = binary_search(A.begin(), A.end(), 7); //True
    present = binary_search(A.begin(), A.end(), 3);      //False

    A.push_back(100);
    present = binary_search(A.begin(), A.end(), 100);

    A.push_back(100);
    A.push_back(100);
    A.push_back(100);
    A.push_back(123);


    auto lower = lower_bound(A.begin(), A.end(), 100);   // >=
    auto upper = upper_bound(A.begin(), A.end(), 100);   // >

    // 1 2 4 5 7 100 100 100 100 123

    cout << "lower of 100 = " <<*lower << " " << "and uper of 100 = " << *upper << endl;



    cout << "frequency of 100 = " << count(A.begin(), A.end(), 100) << endl;

    cout << "lower index 100 = " << (lower - A.begin() + 1) << endl;
    cout << "upper index 100 = " << (upper - A.begin() + 1) << endl;

    cout << "frequency of 100 = " << upper - lower << endl;

    cout << "size of vector = " << A.size() << endl;

    for(auto it : A) cout <<  it << " ";

        cout << endl ;

    for(auto it : A) cout << count(A.begin(), A.end(), it) << " ";


}

output

lower of 100 = 100 and uper of 100 = 123
frequency of 100 = 4
lower index 100 = 6
upper index 100 = 10
frequency of 100 = 4
size of vector = 10
1 2 4 5 7 100 100 100 100 123
1 1 1 1 1 4 4 4 4 1

Vector of Pairs

#include<bits/stdc++.h>
using namespace std;

void printvec(vector<pair<int , int>> &v)

{ v.push_back({3, 5});
    for (int i = 0; i < v.size(); ++i)
    {

        cout << v[i].first << " " << v[i].second << endl;
    }
}
int main()
{
    vector<pair<int, int>> v;
    // v = {{2, 3}, {4, 5}, {7, 6}};
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i)
    {   int x, y;
        cin >> x >> y;
        v.push_back({x, y});
    }
    printvec(v);
}

input

3
5 1
10 3
20 4

output

5 1
10 3
20 4
3 5

Vector of vector

Map

Counting frequencies of array elements

#include<bits/stdc++.h>
using namespace std;
int main()
{int arr[] = { 10, 20, 20, 10, 10, 20, 5, 20 };
int n = sizeof(arr)/sizeof(arr[0]);
    map <int, int> m ;

    for (int i = 0; i < n; ++i)
    {
                m[arr[i]]++;
    }

    for(auto x : m) cout << x.first << " " << x.second <<  endl;
}

output

5 1
10 3
20 4

for string

     #include<bits/stdc++.h>
     using namespace std;
     int main()
     {
        map< string, int> m;
        int n; cin >> n;
        for (int i = 0; i < n; ++i)
        {
            string s; cin >> s;
            m[s]++;
        }
        for(auto pr : m)
         cout << pr.first << " " << pr.second << endl;
     }


input
 5
sed
drw
sed
drw
drw

output

drw 3
sed 2

Non-Repeating Element

#include<bits/stdc++.h>
using namespace std;
int main()
{
    vector<int> v = { 9, 4, 9, 6, 7, 4};
    map<int, int> m;
    for (int i = 0; i < v.size(); ++i)
    {
        m[v[i]]++;
    }
    for(auto x : m)
    {
        if(x.second == 1)
        {
            cout << x.first;
             break;
        }
    }
}

output

6

unordered_map

Counting frequencies of array elements

#include<bits/stdc++.h>
using namespace std;
int main()
{
   unordered_map< int, int> m;
   int n; cin >> n;
   for (int i = 0; i < n; ++i)
   {
       int temp; cin >> temp;
       m[temp]++;
   }
   for(auto pr : m)
    cout << pr.first << " " << pr.second << endl;
}

input

8
10 20 20 10 10 20 5 20

outut

5 1
10 3
20 4

set

rmove dupicate

#include<bits/stdc++.h>
using namespace std;
int main()
{
   set<int> s;
   int n; cin >> n;
   for (int i = 0; i < n; ++i)
   {
       int temp; cin >> temp;
       s.insert(temp);
   }
   for(auto pr : s)
    cout << pr << " ";
    cout << endl;

   for (auto it = s.begin() ; it != s.end(); it++)
   {
       cout << *it << " ";
   }
}

input

8
10 20 20 10 10 20 5 20

output

5 10 20
5 10 20
#include<bits/stdc++.h>
using namespace std;
int main()
{int arr[6] = {4, 2, 3, 3, 2, 4 };
   set<int> s;
   for (int i = 0; i < 6; ++i)
   {
      s.insert(arr[i]);
   }
   for(auto pr : s)
    cout << pr << " ";
    cout << endl;
}

output

2 3 4

Remove duplicates from a given string

#include<bits/stdc++.h>
using namespace std;
int main()
{int hash[123] = {0};
   string s, result = "";
   cin >> s;
   for (int i = 0; i < s.size(); ++i)
   {
      if(hash[s[i]] == 0)
      {
         hash[s[i]] = 1;
         result += s[i];
      }
   }
   cout << result;
}

input

retyyrtywyss

output

retyws

List

#include<bits/stdc++.h>
using namespace std;

int main()
 {
     list<int> list1 = {4, 2, 7, 1, 5};
     list<int> list2 = {8, 5, 9, 6, 3};
     list1.reverse();
     for(auto it : list1)
        cout << it << " ";
    cout << endl;
    list1.merge(list2);
    for(auto it : list1)
        cout << it << " ";
    list1.sort();
    cout << endl;
    for(auto it : list1)
        cout << it << " ";
    list1.unique();
    cout << endl;
    for(auto it : list1)
        cout << it << " ";
    list1.remove(6);
    cout << endl;
    for(auto it : list1)
        cout << it << " ";
    list<int> :: iterator it = list1.begin();
    advance(it, 2);
    list1.insert(it, 5);
    cout << endl;
    for(auto it : list1)
        cout << it << " ";
     return 0;
}

output

5 1 7 2 4
5 1 7 2 4 8 5 9 6 3
1 2 3 4 5 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 7 8 9
1 2 5 3 4 5 7 8 9