Added two pointers codes for interviewbit problems in cpp

TwoPoniters cpp/merge2SortedLists.cpp

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+//Ques Link https://www.interviewbit.com/problems/merge-two-sorted-lists-ii
+/* Given two sorted integer arrays A and B, merge B into A as one sorted array.
+
+ Note: You have to modify the array A to contain the merge of A and B. Do not output anything in your code.
+TIP: C users, please malloc the result into a new array and return the result. 
+If the number of elements initialized in A and B are m and n respectively, the resulting size of array A after your code is executed should be m + n */
+
+//main function has been included to ease readability and for  better understanding
+
+#include <bits/stdc++.h>
+using namespace std;
+void Merge2SortedArrays(vector<int> &A, vector<int> &B)
+{
+
+    vector<int> arr;  //use of additional memory allowed
+    int i = 0, j = 0; //2 pointers to at head of A and B resp.
+    while (i < A.size() && j < B.size())
+    {
+        if (A[i] > B[j])
+        {
+            arr.push_back(B[j]);
+            j++;
+        }
+        else
+        {
+            arr.push_back(A[i]);
+            i++;
+        }
+    }
+    if (i < A.size()) //if elements of A are left, keep pushing them in arr till end
+    {
+        while (i != A.size())
+        {
+            arr.push_back(A[i]);
+            i++;
+        }
+    }
+    if (j < B.size())
+    {
+        while (j != B.size()) //if elements of B are left, keep pushing them in arr till end
+        {
+            arr.push_back(B[j]);
+            j++;
+        }
+    }
+
+    A = arr; //copy vector arr to A to modify A
+}
+
+int main()
+{
+    int size1, size2;
+    cin >> size1 >> size2;
+    vector<int> A(size1), B(size2);
+
+    for (auto &x : A)
+        cin >> x;
+
+    for (auto &xx : B)
+        cin >> xx;
+
+    Merge2SortedArrays(A, B);
+    for (auto &x : A)
+        cout << x << " ";  //array elemets after merge
+    return 0;
+}

TwoPoniters cpp/remove-duplicates-from-sorted-array.cpp

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+//Ques Link: https://www.interviewbit.com/problems/remove-duplicates-from-sorted-array/
+
+/* Remove duplicates from Sorted Array
+Given a sorted array, remove the duplicates in place such that each element appears only once and return the new length.
+
+Note that even though we want you to return the new length, make sure to change the original array as well in place
+
+Do not allocate extra space for another array, you must do this in place with constant memory.
+
+ Example:
+Given input array A = [1,1,2],
+Your function should return length = 2, and A is now [1,2]. */
+
+//main function has been included to ease readability and for  better understanding
+
+#include <bits/stdc++.h>
+using namespace std;
+
+int removeDuplicates(vector<int> &A)
+{
+    if (A.size() == 1)
+        return 1;
+    int i = 1, j = 1;
+    while (i < A.size() && j < A.size())
+    {
+        if (A[i] != A[j])
+        {
+            A[j] = A[i]; //allocate element only if it is unique i.e non duplicate
+        }
+        if (A[j - 1] != A[j]) //array is sorted so we compare adjacent indeces
+        {
+            j++;
+        }
+        i++;
+    }
+    return j;
+}
+int main()
+{
+    int size;
+    cin >> size;
+    vector<int> A(size);
+
+    for (auto &x : A)
+        cin >> x;
+
+    int newlength = removeDuplicates(A);
+
+    cout << "New length after removal of duplicates is " << newlength << endl;
+
+    for (int i = 0; i < newlength; i++)
+        cout << A[i] << " ";
+    return 0;
+}

TwoPoniters cpp/remove-element-from-array.cpp

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+// Ques Link : https: //www.interviewbit.com/problems/remove-element-from-array
+/* Given an array and a value, remove all the instances of that value in the array.
+Also return the number of elements left in the array after the operation.
+It does not matter what is left beyond the expected length.
+
+ Example:
+If array A is [4, 1, 1, 2, 1, 3]
+and value elem is 1,
+then new length is 3, and A is now [4, 2, 3] 
+Try to do it in less than linear additional space complexity. */
+
+//main function has been included to ease readability and for  better understanding
+
+#include <bits/stdc++.h>
+using namespace std;
+int removeElement(vector<int> &A, int B)
+{
+
+    int i = 0, j = 0, duplicates = 0;
+
+    while (i < A.size() && j < A.size())
+    {
+        if (A[i] != B)
+        {
+            A[j++] = A[i];
+        }
+        else
+            duplicates++; //whenever A[i] == B
+        i++;
+    }
+    return A.size() - duplicates;
+}
+
+int main()
+{
+    int size;
+    cin >> size;
+    vector<int> A(size);
+
+    for (auto &x : A)
+        cin >> x;
+    int element;
+    cin >> element;
+    int newlength = removeElement(A, element);
+    cout << "Newlength after removal of element is " << newlength << '\n';
+
+    for (int i = 0; i < newlength; i++)
+        cout << A[i] << " ";
+
+    return 0;
+}