diff --git a/STL 2.0/MAPS/basics.cpp b/STL 2.0/MAPS/basics.cpp
new file mode 100644
index 0000000..c47ee4f
--- /dev/null
+++ b/STL 2.0/MAPS/basics.cpp	
@@ -0,0 +1,52 @@
+/*
+-------------- ORDERED MAPS -----------------
+Time Complexity : O(log(n))
+*/
+
+#include<bits/stdc++.h>
+using namespace std;
+
+void print(map<int,string> &m){
+    cout<<"Size: "<<m.size()<<endl;
+    for(auto &pr : m){
+        cout<<pr.first<<" "<<pr.second<<endl;
+    }
+}
+
+int main(){
+    map<int,string> m;
+    //TIME COMPLEXITY OF INSERTION OF ELEMENTS: O(log(n))--> n: size of MAP
+    m[1] = "abc";
+    m[5] = "cdc";
+    m[3] = "acd";
+    m.insert({4,"abc"});
+    m.insert({8,"abc"});
+
+
+    // map<int,string> :: iterator it;
+    // for(it=m.begin();it!=m.end();it++){
+    //     cout<<it->first<<" "<<it->second<<endl;
+    // }
+
+    print(m);
+
+    //Find function: takes in key value
+    //             : returns an iterator pointing towards the value
+    //TIME COMPLEXITY: O(log(n))
+    // auto it = m.find(9);
+    // if(it == m.end()){
+    //     cout<<"No such value exists"<<endl;
+    // }
+    // else{
+    //     cout<<it->first<<" "<<it->second<<endl;
+    // }
+
+    //ERASE FUNCTION: takes key/iterator as input
+    //              : deletes the specified value if present
+    //TIME COMPLEXITY: O(log(n))
+    // auto it = m.find(3);
+    // m.erase(3);
+    // print(m);
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/MAPS/basics.exe b/STL 2.0/MAPS/basics.exe
new file mode 100644
index 0000000..27c2d97
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diff --git a/STL 2.0/MAPS/nesting.cpp b/STL 2.0/MAPS/nesting.cpp
new file mode 100644
index 0000000..874800c
--- /dev/null
+++ b/STL 2.0/MAPS/nesting.cpp	
@@ -0,0 +1,7 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    map<pair<string,string>,vector<int>> m;
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/MAPS/questions.cpp b/STL 2.0/MAPS/questions.cpp
new file mode 100644
index 0000000..3b05236
--- /dev/null
+++ b/STL 2.0/MAPS/questions.cpp	
@@ -0,0 +1,49 @@
+// // /*
+// // Given N strings. Print unique strings in lexographical order
+// // with their frequency
+// // N<= 10^5
+// // |S| <= 100
+// // */
+
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int N;cin>>N;
+    map<string,int> m;
+    for(int i=0;i<N;i++){
+        string s;
+        cin>>s;
+        // m[i] = s; //making a map
+        m[s]++;
+    }
+//Range Based Loop
+    for(auto pair : m){
+        cout<<pair.first<<" "<<pair.second<<endl;
+    }
+    return 0;
+}
+
+// // -------- MONK and class MARKS: Hackerearth -----------
+//Please search this question on net for more info
+// #include<bits/stdc++.h>
+// using namespace std;
+
+// int main(){
+//     multimap<int,string> list;
+//     int turn;cin>>turn;
+//     while(turn--){
+//         string name; int marks;
+//         cin>>name>>marks;
+//         list.insert({marks,name});
+//     }
+//     map<int,string> :: iterator it;
+//     it  = (--list.end());
+//     while(it!=list.begin()){
+//         cout<<it->second<<" "<<it->first<<endl;
+//         --it;
+//     }
+//     cout<<it->second<<" "<<it->first<<endl;
+//     return 0;
+// }
+
diff --git a/STL 2.0/MAPS/questions.exe b/STL 2.0/MAPS/questions.exe
new file mode 100644
index 0000000..70f5f83
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diff --git a/STL 2.0/MAPS/unordered.cpp b/STL 2.0/MAPS/unordered.cpp
new file mode 100644
index 0000000..497280b
--- /dev/null
+++ b/STL 2.0/MAPS/unordered.cpp	
@@ -0,0 +1,21 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    unordered_map<string,int> m;
+    int N;cin>>N;
+    while(N--){
+        string s;
+        cin>>s;
+        m[s]++;
+    }
+    int q;cin>>q;
+    while(q--){
+        string s;
+        cin>>s;
+        cout<<m[s]<<endl;
+    }
+
+
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/MAPS/unordered.exe b/STL 2.0/MAPS/unordered.exe
new file mode 100644
index 0000000..92222a7
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diff --git a/STL 2.0/SETS/intro.cpp b/STL 2.0/SETS/intro.cpp
new file mode 100644
index 0000000..1f6e9c6
--- /dev/null
+++ b/STL 2.0/SETS/intro.cpp	
@@ -0,0 +1,28 @@
+/*
+--------------- ORDERED SET ----------------
+Time Complexity: O(log(n))
+*/
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    set<string> s;
+    s.insert("abc");
+    s.insert("ghi");
+    s.insert("def");
+    s.insert("jkl");
+    s.insert("mnp");
+    s.insert("abcd");
+    s.insert("sdwefd");
+    auto it = s.find("abc");
+    if(it != s.end()){
+        // cout<<*it<<endl;
+        s.erase(it);
+    }
+
+    for(auto val : s){
+        cout<<val<<endl;
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/SETS/intro.exe b/STL 2.0/SETS/intro.exe
new file mode 100644
index 0000000..6f8158e
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diff --git a/STL 2.0/SETS/questions.cpp b/STL 2.0/SETS/questions.cpp
new file mode 100644
index 0000000..ffa4cf3
--- /dev/null
+++ b/STL 2.0/SETS/questions.cpp	
@@ -0,0 +1,86 @@
+//Monk and magical bag question: HACKEREARTH
+// #include<bits/stdc++.h>
+// using namespace std;
+
+// int main(){
+//     int turn;
+//     cin>>turn;
+//     while(turn--){
+//         long long N , K; //N--> number of bag, K--> total time he has
+//         multiset<long long> candies;
+//         for (long long i = 0; i < N; i++)
+//         {
+//             long long A;
+//             cin>>A;
+//             candies.insert(A);
+//         }
+//         long long eaten = 0;
+//         while(K--){
+//             auto last_it = (--candies.end());
+//             long long candy_ct = *(last_it);
+//             eaten += candy_ct;
+//             candies.erase(last_it);
+//             candies.insert(candy_ct / 2);
+//         }
+//         cout<< eaten << endl;   
+//     }
+    
+//     return 0;
+// }
+
+// ------------- SETS : Hackerrank ---------------
+// #include<bits/stdc++.h>
+// using namespace std;
+
+// int main(){
+//     int query; cin>>query;
+//     set<long long> s;
+//     while(query--){
+//         long long y,x;
+//         cin>>y>>x;
+//         if(y==1){
+//             s.insert(x);
+//         }
+//         else if(y==2){
+//             auto it = s.find(x);
+//             if(it==s.end()){
+//                 continue;
+//             }
+//             else{
+//                 s.erase(x);
+//             }
+//         }
+//         else if(y==3){
+//             auto it = s.find(x);
+//             if(it !=s.end()){
+//                 cout<<"Yes"<<endl;
+//             }
+//             else{
+//                 cout<<"No"<<endl;
+//             }
+//         }
+//     }
+//     return 0;
+// }   
+
+// ------ MONK BIRTHDAY:Hackerearth -----------
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int N;cin>>N;
+    while(N--){
+        set<string> list;
+        int num;cin>>num;
+        while(num--){
+            string name;
+            cin>>name;
+            list.insert(name);
+        }
+        for(auto val : list){
+            cout<< val<<endl;
+        }
+        cout<<endl;
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/SETS/unordered_set.cpp b/STL 2.0/SETS/unordered_set.cpp
new file mode 100644
index 0000000..df8f756
--- /dev/null
+++ b/STL 2.0/SETS/unordered_set.cpp	
@@ -0,0 +1,37 @@
+/*
+------------ Time Complexity ----------------
+O(1)
+*/
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    unordered_set<string> s;
+    int N;
+    cin>>N;
+    for (int i = 0; i < N; i++)
+    {
+        string S;
+        cin>>S;
+        s.insert(S);
+    }
+    int Q;
+    cin>>Q;
+    for (int i = 0; i < Q; i++)
+    {
+        string q;
+        cin>>q;
+        auto it  = s.find(q);
+        if(it!=s.end()){
+            cout<<"PRESENT"<<endl;
+        }
+        else{
+            cout<<"NOT PRESENT"<<endl;
+        }
+
+    }
+    
+    
+
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/SETS/unordered_set.exe b/STL 2.0/SETS/unordered_set.exe
new file mode 100644
index 0000000..bebe40e
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diff --git a/STL 2.0/Sorting/Upper_Lower_Bound.cpp b/STL 2.0/Sorting/Upper_Lower_Bound.cpp
new file mode 100644
index 0000000..c3e542d
--- /dev/null
+++ b/STL 2.0/Sorting/Upper_Lower_Bound.cpp	
@@ -0,0 +1,23 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int n;cin>>n;
+    int a[n];
+    for(int i = 0;i<n;++i){
+        cin>>a[i];
+    }
+    sort(a,a+n);
+    for(int i = 0;i<n;i++){
+        cout<<a[i]<<" ";
+    }
+    cout<<endl;
+    int *ptr = lower_bound(a,a+n,6);
+    int *ptr2 = upper_bound(a,a+n,25);
+    if(ptr==a+n && ptr2==a+n){
+        cout<<"Not Found"<<endl;
+        return 0;
+    }
+    cout<<(*ptr)<<" "<<(*ptr2)<<endl;
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Sorting/Upper_Lower_Bound.exe b/STL 2.0/Sorting/Upper_Lower_Bound.exe
new file mode 100644
index 0000000..8022293
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diff --git a/STL 2.0/Sorting/sort_array.cpp b/STL 2.0/Sorting/sort_array.cpp
new file mode 100644
index 0000000..3e6ab36
--- /dev/null
+++ b/STL 2.0/Sorting/sort_array.cpp	
@@ -0,0 +1,16 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int size;cin>>size;
+    int a[size];
+    for(int i=0;i<size;i++){
+        cin>>a[i]; 
+    }
+    sort(a,a+size);
+    for(int i=0;i<size;i++){
+        cout<<a[i]<<" ";
+    }
+    cout<<endl;
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Sorting/sort_array.exe b/STL 2.0/Sorting/sort_array.exe
new file mode 100644
index 0000000..62b1e43
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diff --git a/STL 2.0/Sorting/sort_vector.cpp b/STL 2.0/Sorting/sort_vector.cpp
new file mode 100644
index 0000000..b00b3b6
--- /dev/null
+++ b/STL 2.0/Sorting/sort_vector.cpp	
@@ -0,0 +1,16 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int n;cin>>n;
+    vector<int> a(n);
+    for(int i = 0;i<n;i++){
+        cin>>a[i];
+    }
+    sort(a.begin(),a.end());
+    for(int i = 0;i<n;i++){
+        cout<<a[i]<<" ";
+    }
+    cout<<endl;
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Sorting/sort_vector.exe b/STL 2.0/Sorting/sort_vector.exe
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index 0000000..a334391
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diff --git a/STL 2.0/Stacks & Queues/queue_intro.cpp b/STL 2.0/Stacks & Queues/queue_intro.cpp
new file mode 100644
index 0000000..27dbb2c
--- /dev/null
+++ b/STL 2.0/Stacks & Queues/queue_intro.cpp	
@@ -0,0 +1,16 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    queue<string> q;
+    q.push("abc"); //Frontmost element
+    q.push("bcd");
+    q.push("dfr");
+    q.push("wer");
+    q.push("asx");//Last element
+    while(!q.empty()){
+        cout<<q.front()<<" ";
+        q.pop();
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Stacks & Queues/queue_intro.exe b/STL 2.0/Stacks & Queues/queue_intro.exe
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diff --git a/STL 2.0/Stacks & Queues/stack_intro.cpp b/STL 2.0/Stacks & Queues/stack_intro.cpp
new file mode 100644
index 0000000..3a4c270
--- /dev/null
+++ b/STL 2.0/Stacks & Queues/stack_intro.cpp	
@@ -0,0 +1,15 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    stack<int> s;
+    s.push(2); //First Element
+    s.push(3);
+    s.push(4);
+    s.push(5); //Topmost Element
+    while(!s.empty()){
+        cout<<s.top()<<endl;
+        s.pop();
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Stacks & Queues/stack_intro.exe b/STL 2.0/Stacks & Queues/stack_intro.exe
new file mode 100644
index 0000000..a20bc4f
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diff --git a/STL 2.0/Stacks & Queues/stack_ques.cpp b/STL 2.0/Stacks & Queues/stack_ques.cpp
new file mode 100644
index 0000000..2658a58
--- /dev/null
+++ b/STL 2.0/Stacks & Queues/stack_ques.cpp	
@@ -0,0 +1,83 @@
+// ------ BALANCED BRACKETS -------------
+// #include<bits/stdc++.h>
+// using namespace std;
+
+// unordered_map<char,int> symbols = {{'[',-1},{'(',-2},{'{',-3},{']',1},{')',2},{'}',3}};
+
+// string isBalanced(string s) {
+//     stack<char>st;
+//     for(char bracket : s){
+//         if(symbols[bracket]<0){
+//             st.push(bracket);
+//         }
+//         else{
+//             if(st.empty()) return "NO";
+//             char top = st.top();
+//             st.pop();
+//             if(symbols[top] + symbols[bracket]!=0){
+//                 return "NO";
+//             }
+//         }
+//     }
+//     if(st.empty()){
+//         return "YES";
+//     }
+//     return "NO";
+
+// }
+
+// int main(){
+//     int turn;cin>>turn;
+//     while(turn--){
+//         string s;
+//         cin>>s;
+//         cout<<isBalanced(s)<<endl;
+//     }
+//     return 0;
+// }
+
+//--------- NEXT GREATER ELEMENT -----------
+//Question: Suppose we are given an array [4,5,2,25,7,8]
+//For each element,write next greater element on right of that element or replace
+//with -1
+//Here our required output: [5,25,25,-1,8,-1]
+
+#include<bits/stdc++.h>
+using namespace std;
+
+vector<int> NGE(vector<int> v){
+    vector<int> nge(v.size());
+    stack<int> st;
+    for (int i = 0; i < v.size(); i++)
+    {
+        while (!st.empty() && v[i]>v[st.top()])
+        {
+            nge[st.top()] = i;
+            st.pop();
+        }
+        st.push(i);  
+    }
+    while(!st.empty()){
+        nge[st.top()] = -1;
+        st.pop();
+    }
+    return nge;
+    
+
+}
+
+int main(){
+    int n;cin>>n;
+    vector<int> v(n);
+    for(int i=0;i<n;i++){
+        cin>>v[i];
+    }
+
+    vector<int> nge = NGE(v);
+    for (int i = 0; i < n; i++)
+    {
+        cout<<v[i]<<" "<<(nge[i] == -1 ? -1 : v[nge[i]])<<endl;
+    }
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Stacks & Queues/stack_ques.exe b/STL 2.0/Stacks & Queues/stack_ques.exe
new file mode 100644
index 0000000..1381e0a
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diff --git a/STL 2.0/Vectors and Pairs/Nesting_vect.cpp b/STL 2.0/Vectors and Pairs/Nesting_vect.cpp
new file mode 100644
index 0000000..857c480
--- /dev/null
+++ b/STL 2.0/Vectors and Pairs/Nesting_vect.cpp	
@@ -0,0 +1,72 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+void printVec(vector<int>&v){
+    cout<<"SIZE: "<<v.size()<<endl;
+    for (int i = 0; i < v.size(); i++)
+    {
+        cout<<v[i]<<" ";
+    }
+    cout<<endl;
+} 
+
+int main(){
+    //********* PAIRS of VECTORS ************
+    // vector<pair<int,int>> v; //= {{1,2},{3,4},{4,5}};
+    // printVec(v);
+    // int n;
+    // cin>>n;
+    // for (int i = 0; i < n; i++)
+    // {
+    //     int x,y;
+    //     cin>>x>>y;
+    //     v.push_back({x,y});
+    // }
+    // printVec(v);
+
+    // ************ ARRAYS of VECTORS *************
+    // int N;  //declaring how many vectors we want
+    // cin>>N;
+    // vector<int> v[N]; //creating N vector-array
+
+    // for (int i = 0; i < N; i++)
+    // {
+    //     int n;cin>>n; //input size of each vector;
+    //     for (int j = 0; j < n; j++)
+    //     {
+    //         int num;
+    //         cin>>num;
+    //         v[i].push_back(num);
+    //     }
+        
+    // }
+    // for (int i = 0; i < N; i++)
+    // {
+    //     printVec(v[i]);
+    // }
+
+    // ********** VECTOR of VECTOR
+    int N; //how many nested vectors we want.
+    cin>>N;
+    vector<vector<int>> v; //we will get N vectors;
+
+    for(int i=0;i<N;i++){
+        //taking size of each vector;
+        int size;cin>>size;
+        vector<int> temp;
+        for(int j=0;j<size;j++){
+            int num;cin>>num;
+            // v[i].push_back(num); //This statement isn't allowed as v[i] doesnot exist rn.
+            temp.push_back(num);
+        }
+        v.push_back(temp);
+    }
+
+    for (int i = 0; i < v.size(); i++)
+    {
+        printVec(v[i]);
+    }
+    
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Vectors and Pairs/Nesting_vect.exe b/STL 2.0/Vectors and Pairs/Nesting_vect.exe
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diff --git a/STL 2.0/Vectors and Pairs/iterator.cpp b/STL 2.0/Vectors and Pairs/iterator.cpp
new file mode 100644
index 0000000..8778571
--- /dev/null
+++ b/STL 2.0/Vectors and Pairs/iterator.cpp	
@@ -0,0 +1,34 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    vector<int> v ={2,3,4,5,6,7};
+    // vector<int> :: iterator it = v.begin();
+    // for(int i=0;i<v.size();i++){
+    //     cout<<i+1<<" element in vector: "<<*(it+i)<<endl;
+    // }
+    // for (it = v.begin(); it!=v.end(); it++)
+    // {
+    //     cout<<*it<<endl;
+    // }
+
+    vector<pair<int,int>> v_p = {{1,2},{3,4},{5,6}};
+    // vector<pair<int,int>> :: iterator it_p;
+    // for (it_p = v_p.begin(); it_p!=v_p.end(); it_p++)
+    // {
+    //     // cout<<(*(it_p)).first<<" "<<(*(it_p)).second<<endl;
+    //     cout<<(it_p)->first<<" "<<(it_p)->second<<endl;
+    // }
+
+    //RANGE BASED LOOP
+    for(int val : v){
+        cout<<val<<" ";
+    }
+    cout<<endl;
+
+    for(pair<int,int> val : v_p){
+        cout<<val.first<<" "<<val.second<<endl;
+    }
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/STL 2.0/Vectors and Pairs/iterator.exe b/STL 2.0/Vectors and Pairs/iterator.exe
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diff --git a/STL 2.0/Vectors and Pairs/vectors_pair.cpp b/STL 2.0/Vectors and Pairs/vectors_pair.cpp
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+++ b/STL 2.0/Vectors and Pairs/vectors_pair.cpp	
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+// ***************** PAIRS *********************
+// #include<bits/stdc++.h>
+// using namespace std;
+
+// int main(){
+    //Making a pair
+//     pair<int,string> p;
+
+    //Ways to input in a pair
+//     p = {2,"abc"};
+//     p = make_pair(2,"abc");
+
+        //Making array pairs
+//     int a[3] = {1,2,3};
+//     int b[3] = {10,20,30};
+//     pair<int,int>p[3];
+//     p[0] = {a[0] , b[0]};
+//     p[1] = {a[1] , b[1]};
+//     p[2] = {a[2] , b[2]};
+//     swap(p[0],p[2]);
+//     for (int i = 0; i < 3; i++)
+//     {
+//         cout<<p[i].first<<" "<<p[i].second<<endl; 
+//     }
+    
+//     return 0;
+// }
+
+// **************** VECTORS *****************
\ No newline at end of file
diff --git a/STL 2.0/Vectors and Pairs/vectors_pair.exe b/STL 2.0/Vectors and Pairs/vectors_pair.exe
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