# Sets-STL C++

### Problem Statement :

```Sets are a part of the C++ STL. Sets are containers that store unique elements following a specific order. Here are some of the frequently used member functions of sets:

Declaration:

set<int>s; //Creates a set of integers.

Size:

int length=s.size(); //Gives the size of the set.

Insert:

s.insert(x); //Inserts an integer x into the set s.

Erasing an element:

s.erase(val); //Erases an integer val from the set s.

Finding an element:

set<int>::iterator itr=s.find(val); //Gives the iterator to the element val if it is found otherwise returns s.end() .
Ex: set<int>::iterator itr=s.find(100); //If 100 is not present then it==s.end().

To know more about sets click Here. Coming to the problem, you will be given  Q queries. Each query is of one of the following three types:

1 x: Add an element x to the set.
2 x: Delete an element x from the set. (If the number x is not present in the set, then do nothing).
3 x: If the number x is present in the set, then print "Yes"(without quotes) else print "No"(without quotes).

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. Each query consists of two integers y and x where y is the type of the query and x is an integer.

Constraints

1 <=  Q  <= 10^5
1 <=   y  <= 3
1 <=   x  <= 10^9

Output Format

For queries of type 3 print "Yes"(without quotes) if the number x is present in the set and if the number is not present, then print "No"(without quotes).
Each query  of type 3 should be printed in a new line.```

### Solution :

```                            ```Solution in C :

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

int main() {
int c,t,n;
scanf("%d",&n);
set<int> ns;
while(n--) {
scanf("%d %d",&c,&t);
switch(c) {
case 1:
ns.insert(t);
break;
case 2:
ns.erase(t);
break;
case 3:
if (ns.find(t)!=ns.end())
cout << "Yes"<<endl;
else
cout <<"No"<<endl;
break;
default:
cout<<"invalid switch value: "<<c<<endl;

}
}

return 0;
}```
```

## Get Node Value

This challenge is part of a tutorial track by MyCodeSchool Given a pointer to the head of a linked list and a specific position, determine the data value at that position. Count backwards from the tail node. The tail is at postion 0, its parent is at 1 and so on. Example head refers to 3 -> 2 -> 1 -> 0 -> NULL positionFromTail = 2 Each of the data values matches its distance from the t

## Delete duplicate-value nodes from a sorted linked list

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## Cycle Detection

A linked list is said to contain a cycle if any node is visited more than once while traversing the list. Given a pointer to the head of a linked list, determine if it contains a cycle. If it does, return 1. Otherwise, return 0. Example head refers 1 -> 2 -> 3 -> NUL The numbers shown are the node numbers, not their data values. There is no cycle in this list so return 0. head refer

## Find Merge Point of Two Lists

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## Inserting a Node Into a Sorted Doubly Linked List

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## Reverse a doubly linked list

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