DSA algorithms

MergeSort.cpp

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+#include<iostream>
+using namespace std;
+void swapping(int &a, int &b) {     //swap the content of a and b
+   int temp;
+   temp = a;
+   a = b;
+   b = temp;
+}
+void display(int *array, int size) {
+   for(int i = 0; i<size; i++)
+      cout << array[i] << " ";
+   cout << endl;
+}
+void merge(int *array, int l, int m, int r) {
+   int i, j, k, nl, nr;
+   //size of left and right sub-arrays
+   nl = m-l+1; nr = r-m;
+   int larr[nl], rarr[nr];
+   //fill left and right sub-arrays
+   for(i = 0; i<nl; i++)
+      larr[i] = array[l+i];
+   for(j = 0; j<nr; j++)
+      rarr[j] = array[m+1+j];
+   i = 0; j = 0; k = l;
+   //marge temp arrays to real array
+   while(i < nl && j<nr) {
+      if(larr[i] <= rarr[j]) {
+         array[k] = larr[i];
+         i++;
+      }else{
+         array[k] = rarr[j];
+         j++;
+      }
+      k++;
+   }
+   while(i<nl) {       //extra element in left array
+      array[k] = larr[i];
+      i++; k++;
+   }
+   while(j<nr) {     //extra element in right array
+      array[k] = rarr[j];
+      j++; k++;
+   }
+}
+void mergeSort(int *array, int l, int r) {
+   int m;
+   if(l < r) {
+      int m = l+(r-l)/2;
+      // Sort first and second arrays
+      mergeSort(array, l, m);
+      mergeSort(array, m+1, r);
+      merge(array, l, m, r);
+   }
+}
+int main() {
+   int n;
+   cout << "Enter the number of elements: ";
+   cin >> n;
+   int arr[n];     //create an array with given number of elements
+   cout << "Enter elements:" << endl;
+   for(int i = 0; i<n; i++) {
+      cin >> arr[i];
+   }
+   cout << "Array before Sorting: ";
+   display(arr, n);
+   mergeSort(arr, 0, n-1);     //(n-1) for last index
+   cout << "Array after Sorting: ";
+   display(arr, n);
+}

QuickSort.cpp

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+// Quick sort in C++
+
+#include <iostream>
+using namespace std;
+
+// function to swap elements
+void swap(int *a, int *b) {
+  int t = *a;
+  *a = *b;
+  *b = t;
+}
+
+// function to print the array
+void printArray(int array[], int size) {
+  int i;
+  for (i = 0; i < size; i++)
+    cout << array[i] << " ";
+  cout << endl;
+}
+
+// function to rearrange array (find the partition point)
+int partition(int array[], int low, int high) {
+
+  // select the rightmost element as pivot
+  int pivot = array[high];
+
+  // pointer for greater element
+  int i = (low - 1);
+
+  // traverse each element of the array
+  // compare them with the pivot
+  for (int j = low; j < high; j++) {
+    if (array[j] <= pivot) {
+
+      // if element smaller than pivot is found
+      // swap it with the greater element pointed by i
+      i++;
+
+      // swap element at i with element at j
+      swap(&array[i], &array[j]);
+    }
+  }
+
+  // swap pivot with the greater element at i
+  swap(&array[i + 1], &array[high]);
+
+  // return the partition point
+  return (i + 1);
+}
+
+void quickSort(int array[], int low, int high) {
+  if (low < high) {
+
+    // find the pivot element such that
+    // elements smaller than pivot are on left of pivot
+    // elements greater than pivot are on righ of pivot
+    int pi = partition(array, low, high);
+
+    // recursive call on the left of pivot
+    quickSort(array, low, pi - 1);
+
+    // recursive call on the right of pivot
+    quickSort(array, pi + 1, high);
+  }
+}
+
+// Driver code
+int main() {
+  int data[] = {8, 7, 6, 1, 0, 9, 2};
+  int n = sizeof(data) / sizeof(data[0]);
+
+  cout << "Unsorted Array: \n";
+  printArray(data, n);
+
+  // perform quicksort on data
+  quickSort(data, 0, n - 1);
+
+  cout << "Sorted array in ascending order: \n";
+  printArray(data, n);
+}