Create Mergesort.cpp

Solved-Problems/Mergesort.cpp

@@ -0,0 +1,91 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// Merges two subarrays of arr[].
+// First subarray is arr[left..mid]
+// Second subarray is arr[mid+1..right]
+void merge(vector<int>& arr, int left, 
+                     int mid, int right)
+{
+    int n1 = mid - left + 1;
+    int n2 = right - mid;
+
+    // Create temp vectors
+    vector<int> L(n1), R(n2);
+
+    // Copy data to temp vectors L[] and R[]
+    for (int i = 0; i < n1; i++)
+        L[i] = arr[left + i];
+    for (int j = 0; j < n2; j++)
+        R[j] = arr[mid + 1 + j];
+
+    int i = 0, j = 0;
+    int k = left;
+
+    // Merge the temp vectors back 
+    // into arr[left..right]
+    while (i < n1 && j < n2) {
+        if (L[i] <= R[j]) {
+            arr[k] = L[i];
+            i++;
+        }
+        else {
+            arr[k] = R[j];
+            j++;
+        }
+        k++;
+    }
+
+    // Copy the remaining elements of L[], 
+    // if there are any
+    while (i < n1) {
+        arr[k] = L[i];
+        i++;
+        k++;
+    }
+
+    // Copy the remaining elements of R[], 
+    // if there are any
+    while (j < n2) {
+        arr[k] = R[j];
+        j++;
+        k++;
+    }
+}
+
+// begin is for left index and end is right index
+// of the sub-array of arr to be sorted
+void mergeSort(vector<int>& arr, int left, int right)
+{
+    if (left >= right)
+        return;
+
+    int mid = left + (right - left) / 2;
+    mergeSort(arr, left, mid);
+    mergeSort(arr, mid + 1, right);
+    merge(arr, left, mid, right);
+}
+
+// Function to print a vector
+void printVector(vector<int>& arr)
+{
+    for (int i = 0; i < arr.size(); i++)
+        cout << arr[i] << " ";
+    cout << endl;
+}
+
+// Driver code
+int main()
+{
+    vector<int> arr = { 12, 11, 13, 5, 6, 7 };
+    int n = arr.size();
+
+    cout << "Given vector is \n";
+    printVector(arr);
+
+    mergeSort(arr, 0, n - 1);
+
+    cout << "\nSorted vector is \n";
+    printVector(arr);
+    return 0;
+}