Merge pull request Algo-Phantoms#2000 from Harikrishnan6336/In_Place_…

…Merge_Sort

In Place Merge Sort in C++

Algorithm/Searching_Sorting/readme.md

@@ -70,6 +70,7 @@ Following are the types of searches which we will be discussing in this book.
 * Fibonacci Search ----> [C++](Algorithm/Searching_Sorting/fibonacci_search.cpp)
 * Find peak element using binary search ----> [Python](/Code/Python/peak_element.py)
 * Heap Sort ----> [C++](/Code/C++/heap_sort.cpp)
+* In Place Merge Sort ----> [C++](/Code/C++/in_place_merge_sort.cpp)
 * Insertion Sort ----> [C++](/Code/C++/insertion_sort.cpp)
 * Linear Search ----> [Python](/Code/Python/linearsearch.py)
 * Merge Sort ----> [C++](/Code/C++/merge_sort.cpp)
@@ -84,5 +85,5 @@ Following are the types of searches which we will be discussing in this book.
 * Staircase Search ----> [C++](/Code/C++/staircase_search.cpp)
 * Three Way Merge Sort ----> [C++](/Code/C++/three_way_merge_sort.cpp)
 * Tim Sort ----> [C++](/Code/C++/tim_sort.cpp)
-* Binary Search ----> [Java](Algorithm/Searching_Sorting/Binary_search.java)
+
 

Code/C++/in_place_merge_sort.cpp

@@ -0,0 +1,111 @@
+// C++ program to implement In Place Merge Sort
+#include <bits/stdc++.h>
+using namespace std;
+
+
+// Merges two subarrays in an inPlace mode
+void inplace_merge(int arr[], int beg, int mid, int end)
+{
+    int sec_beg = mid + 1;
+
+    // If the last element of the first subarray is greater than the first element
+    // of the second subarray, then the both arrays are already in sorted order
+    if (arr[mid] <= arr[sec_beg])
+    {
+        return;
+    }
+
+    // beg points to the beginning of the first subarray and sec_beg to that of second
+    while (beg <= mid && sec_beg <= end)
+    {
+
+        // Compare the first element of both the subarrays, to find the smaller one
+        //If the first one is smaller, increment beg
+        if (arr[beg] <= arr[sec_beg])
+        {
+            beg++;
+        }
+        else
+        {
+            int pos = sec_beg;
+            int val = arr[sec_beg];
+
+            // Else Shift all the elements to the right till the second element and
+            // place the second element at the first element's position
+            for (; pos != beg; pos--)
+            {
+                arr[pos] = arr[pos - 1];
+            }
+            arr[beg] = val;
+
+            // Increment the pointers
+            beg++;
+            mid++;
+            sec_beg++;
+        }
+    }
+}
+
+void merge_sort(int arr[], int beg, int end)
+{
+    if (beg < end)
+    {
+
+        //Finds the mid index of the concerned array
+        int mid = beg + (end - beg)/2;
+
+        // Recursively call the function for the first and the second part of the array
+        merge_sort(arr, beg, mid);
+        merge_sort(arr, mid + 1, end);
+
+        // Merge the two arrays
+        inplace_merge(arr, beg, mid, end);
+    }
+}
+
+int main()
+{
+    int n;
+    cout << "\nHow many numbers do you want to sort? ";
+    cin >> n;
+    int arr[n];
+
+    if (n <= 0)
+    {
+        cout << "There are no numbers to sort!!!";
+        return 0;
+    }
+    // Input the numbers to sort
+    cout << "Enter the numbers: ";
+    for (int i = 0; i < n; i++)
+        cin >> arr[i];
+
+    merge_sort(arr, 0, n - 1);
+
+    cout << "The numbers in sorted order is: ";
+    // Print the sorted array
+    for (int i = 0; i < n; i++)
+        printf(" %d ", arr[i]);
+    cout << "\n";
+
+    return 0;
+}
+
+/*
+SAMPLE INPUT AND OUTPUT
+
+SAMPLE 1
+
+How many numbers do you want to sort? 5
+Enter the numbers: 1 3 5 2 4
+The numbers in sorted order is:  1  2  3  4  5
+
+SAMPLE 2
+How many numbers do you want to sort? 0
+There are no numbers to sort!!!
+*/
+
+// Time Complexity: O(n^2) where n is the number of elements
+// Space Complexity: O(n)
+
+