diff --git a/Famous-Coding-Interview-Problems/MergeKSortedList.cpp b/Famous-Coding-Interview-Problems/MergeKSortedList.cpp
new file mode 100644
index 0000000..d7e349b
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/MergeKSortedList.cpp
@@ -0,0 +1,87 @@
+
+//  4. link : [ https://leetcode.com/problems/merge-k-sorted-lists ]
+
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    
+ 
+ListNode* merge(ListNode* l1, ListNode* l2) {
+        if(l1 == NULL && l2 == NULL)
+             return NULL;
+         if(l1==NULL)
+               return l2;
+          if(l2==NULL)
+            return l1;
+    
+        ListNode* temp1 = l1;
+        ListNode* temp2 = l2;
+        
+        ListNode* tail = new ListNode(0);
+        ListNode* head = tail;
+        
+        
+        while(temp1 && temp2){
+            if(temp1->val <= temp2->val){
+                ListNode* newNode = new ListNode(temp1->val);
+                tail->next = newNode;
+                tail = newNode;
+                temp1 = temp1->next;
+            }else{
+                ListNode* newNode = new ListNode(temp2->val);
+                tail->next = newNode;
+                tail = newNode;
+                temp2 = temp2->next;
+            }
+        }
+        
+        while(temp1){
+            ListNode* newNode = new ListNode(temp1->val);
+            tail->next = newNode;
+            tail = newNode;
+            temp1 = temp1->next;
+        }
+        
+        while(temp2){
+            ListNode* newNode = new ListNode(temp2->val);
+            tail->next = newNode;
+            tail = newNode;
+            temp2 = temp2->next;
+        }
+       
+        return (head->next);   
+}
+    
+    ListNode* helper(vector<ListNode*>& lists, int l, int r){
+        if(l == r)
+            return lists[l];
+        
+        int mid = l+(r-l)/2;
+        
+       ListNode* h1 = helper(lists,l,mid);
+       ListNode* h2 = helper(lists,mid+1,r);
+       
+       return merge(h1,h2);
+        
+    }
+    
+    ListNode* mergeKLists(vector<ListNode*>& lists) {
+        if(lists.size() == 0)
+            return NULL;
+       
+        int l = 0;
+        int r = lists.size()-1;
+        
+        return helper(lists,l,r);
+    }
+};
\ No newline at end of file
diff --git a/Famous-Coding-Interview-Problems/firstAndLastPos.cpp b/Famous-Coding-Interview-Problems/firstAndLastPos.cpp
new file mode 100644
index 0000000..cb1c0bb
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/firstAndLastPos.cpp
@@ -0,0 +1,77 @@
+
+//  7 . link : [ https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array ]
+
+#include<bits/stdc++.h>
+using namespace std;
+ 
+ int binarySearch(vector<int>& nums, int l,int r, int target){
+        if(l>r){
+            return -1;
+        }
+        int mid =  l+(r-l)/2;
+        
+        if(nums[mid] == target)
+            return mid;
+        else if(nums[mid] > target)
+            return binarySearch(nums,l,mid-1,target);
+        else
+            return binarySearch(nums,mid+1,r,target);
+    }
+    
+    vector<int> searchRange(vector<int>& nums, int target) {
+        int pos = binarySearch(nums,0,nums.size()-1, target);
+        
+        if(pos < 0)
+            return {-1,-1};
+        int left = pos;
+        int right = pos;
+        
+        while(left > 0){
+            if(nums[left-1] != target)
+                break;
+            left--;
+        }
+        while(right < nums.size()-1){
+            if(nums[right+1] != target)
+                break;
+            right++;
+        }
+        
+        return {left,right};
+    }
+
+/*
+1
+9
+5 7 7 8 8 8 9 10 11
+8
+
+
+3 5
+*/
+
+int main(){
+    #ifndef ONLINE_JUDGE
+        freopen("input.txt", "r", stdin);
+        freopen("output.txt", "w", stdout);
+    #endif
+
+        int test;
+        cin >> test;
+
+        while(test--){
+            int n; 
+            cin >> n;
+            vector<int> arr(n);
+            for(int i=0; i<n; i++)
+                 cin >> arr[i];
+
+            int target ; cin >> target;
+
+            vector<int> index =  searchRange(arr , target);
+            cout << index[0] << " " << index[1] << endl;;     
+        }
+
+
+    return 0;    
+}
\ No newline at end of file
diff --git a/Famous-Coding-Interview-Problems/longestWord.cpp b/Famous-Coding-Interview-Problems/longestWord.cpp
new file mode 100644
index 0000000..e2b92a5
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/longestWord.cpp
@@ -0,0 +1,45 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+string LongestWord(string sen) {
+  
+  // code goes here  
+  string ans="";
+  string currStr="";
+
+
+  for(int i=0; i<sen.size(); i++){
+    
+    if(sen[i] >= 'a' && sen[i] <= 'z'){
+      currStr += sen[i];
+    }else{
+      if(currStr.size() > ans.size()){
+        ans = currStr;
+        currStr = "";
+      }
+    }
+  }
+
+  if(currStr.size() > ans.size())
+    ans = currStr;
+
+  return ans;
+
+}
+
+
+
+int main(){
+    #ifndef ONLINE_JUDGE
+        freopen("input.txt", "r", stdin);
+        freopen("output.txt", "w", stdout);
+    #endif
+
+    cout << LongestWord("fun&!! time");
+
+    string s = "fun&!! time";
+
+    
+    return 0;    
+
+}
\ No newline at end of file
diff --git a/Famous-Coding-Interview-Problems/mergeTwoSortedList.cpp b/Famous-Coding-Interview-Problems/mergeTwoSortedList.cpp
new file mode 100644
index 0000000..957d3dc
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/mergeTwoSortedList.cpp
@@ -0,0 +1,123 @@
+
+//  3. link : [ https://leetcode.com/problems/merge-two-sorted-lists ]
+
+#include<bits/stdc++.h>
+using namespace std;
+
+// node class
+class ListNode{
+    public:
+    int val;
+    ListNode* next;
+
+    ListNode(int data){
+        this->val = data;
+        next = NULL;
+    }
+
+};
+
+
+ ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
+        ListNode* temp1 = l1;
+        ListNode* temp2 = l2;
+        
+        ListNode* tail = new ListNode(0);
+        ListNode* head = tail;
+        
+        
+        while(temp1 && temp2){
+            if(temp1->val <= temp2->val){
+                ListNode* newNode = new ListNode(temp1->val);
+                tail->next = newNode;
+                tail = newNode;
+                temp1 = temp1->next;
+            }else{
+                ListNode* newNode = new ListNode(temp2->val);
+                tail->next = newNode;
+                tail = newNode;
+                temp2 = temp2->next;
+            }
+        }
+        
+        while(temp1){
+            ListNode* newNode = new ListNode(temp1->val);
+            tail->next = newNode;
+            tail = newNode;
+            temp1 = temp1->next;
+        }
+        
+        while(temp2){
+            ListNode* newNode = new ListNode(temp2->val);
+            tail->next = newNode;
+            tail = newNode;
+            temp2 = temp2->next;
+        }
+       
+        return head->next;   
+}
+
+ListNode* takeInput(){
+    ListNode* head = NULL;
+    ListNode* tail = NULL;
+    
+    int data;
+    while(cin >> data && data != -1){
+        ListNode* node = new ListNode(data);
+        if(head == NULL){
+            head = node;
+            tail = node;
+        }else{
+            tail->next = node;
+            tail = node;
+        }
+    }
+    return head;
+}
+
+void print(ListNode* head){
+    if(head == NULL)
+     return;
+
+     while(head){
+         cout << head->val << " ";
+         head = head->next;
+     }
+     cout << endl;
+}
+
+
+
+/*
+1
+1
+1 3 4 5 6 -1
+-2 -4 3 7 9  -1 
+
+-2 -4 1 3 3 4 5 6 7 9 
+
+*/
+
+int main(){
+    #ifndef ONLINE_JUDGE
+        freopen("input.txt", "r", stdin);
+        freopen("output.txt", "w", stdout);
+    #endif
+
+        int test;
+        cin >> test;
+
+        while(test--){
+
+           ListNode* l1 = takeInput();
+           ListNode* l2 = takeInput();
+
+           ListNode* head = mergeTwoLists(l1, l2);
+           print(head);
+
+
+        }
+
+
+    return 0;    
+}
\ No newline at end of file
diff --git a/Famous-Coding-Interview-Problems/rainWaterTrapping.cpp b/Famous-Coding-Interview-Problems/rainWaterTrapping.cpp
new file mode 100644
index 0000000..a223247
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/rainWaterTrapping.cpp
@@ -0,0 +1,61 @@
+
+//  5. link : [ https://leetcode.com/problems/trapping-rain-water ]
+
+#include<bits/stdc++.h>
+using namespace std;
+
+
+int trap(vector<int>& height) {
+       int n = height.size();
+        if(n<=2)
+            return 0;
+        
+        int left[n];
+        int right[n];
+        
+        left[0] = height[0];
+        for(int i=1; i<n; i++)
+          left[i] = max(left[i-1],height[i]);
+        
+        right[n-1] = height[n-1];
+        for(int i=n-2; i>=0; i--)
+            right[i] = max(right[i+1],height[i]);
+        
+        int water=0;
+        for(int i=0; i<n; i++){
+            water += min(left[i],right[i])-height[i];
+        }
+        return water;
+}
+
+/*
+1
+12
+0 1 0 2 1 0 1 3 2 1 2 1
+
+6
+
+*/
+
+int main(){
+    #ifndef ONLINE_JUDGE
+        freopen("input.txt", "r", stdin);
+        freopen("output.txt", "w", stdout);
+    #endif
+
+        int test;
+        cin >> test;
+
+        while(test--){
+            int n; 
+            cin >> n;
+            vector<int> arr(n);
+            for(int i=0; i<n; i++)
+                 cin >> arr[i];
+
+            cout << trap(arr) << endl;;     
+        }
+
+
+    return 0;    
+}
\ No newline at end of file
diff --git a/Famous-Coding-Interview-Problems/threeSum.cpp b/Famous-Coding-Interview-Problems/threeSum.cpp
new file mode 100644
index 0000000..279a3ad
--- /dev/null
+++ b/Famous-Coding-Interview-Problems/threeSum.cpp
@@ -0,0 +1,76 @@
+
+//  2. link : [ https://leetcode.com/problems/3sum ]
+
+#include<bits/stdc++.h>
+using namespace std;
+
+vector<vector<int>> threeSum(vector<int>& nums){
+         int n = nums.size();
+        set <vector<int>> s;
+        vector<vector<int>> res;
+        
+        sort(nums.begin(), nums.end());
+        
+        for(int i=0; i<n-2; i++){
+           
+            int j = i+1;
+            int k = n-1;
+            
+            while(j<k){
+                long long  sum = nums[i]+nums[j]+nums[k];
+                if(sum == 0){
+                     s.insert({nums[i],nums[j],nums[k]});
+                    j++; k--;
+                }
+                else if(sum < 0)
+                    j++;
+                else
+                    k--;
+            }
+        }
+        
+         auto it = s.begin();
+         while(it != s.end()){
+            res.push_back(*it);
+            it++;
+         }
+        return res;
+}
+
+
+/*
+1
+6
+-1 0 2 -1 -4 1
+
+-1 -1 2
+-1 0 1
+*/
+
+int main(){
+    #ifndef ONLINE_JUDGE
+        freopen("input.txt", "r", stdin);
+        freopen("output.txt", "w", stdout);
+    #endif
+
+        int test;
+        cin >> test;
+
+        while(test--){
+            int n; 
+            cin >> n;
+            vector<int> arr(n);
+            for(int i=0; i<n; i++)
+                 cin >> arr[i];
+
+            vector<vector<int>> res =  threeSum(arr);
+            for(int i=0; i<res.size(); i++){
+                 for(int j=0; j<res[i].size(); j++)
+                   cout << res[i][j] << " ";
+               cout << endl;  
+            }      
+        }
+
+
+    return 0;    
+}
\ No newline at end of file