Add mergesort in C

C/MergeSort.c

@@ -0,0 +1,96 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+// Merges two subarrays of arr[].
+// First subarray is arr[l..m]
+// Second subarray is arr[m+1..r]
+void merge(int arr[], int l, int m, int r)
+{
+    int i, j, k;
+    int n1 = m - l + 1;
+    int n2 = r - m;
+
+    /* create temp arrays */
+    int L[n1], R[n2];
+
+    /* Copy data to temp arrays L[] and R[] */
+    for (i = 0; i < n1; i++)
+        L[i] = arr[l + i];
+    for (j = 0; j < n2; j++)
+        R[j] = arr[m + 1 + j];
+
+    /* Merge the temp arrays back into arr[l..r]*/
+    i = 0; // Initial index of first subarray
+    j = 0; // Initial index of second subarray
+    k = l; // Initial index of merged subarray
+    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++;
+    }
+}
+
+/* l is for left index and r is right index of the
+sub-array of arr to be sorted */
+void mergeSort(int arr[], int l, int r)
+{
+    if (l < r) {
+        // Same as (l+r)/2, but avoids overflow for
+        // large l and h
+        int m = l + (r - l) / 2;
+
+        // Sort first and second halves
+        mergeSort(arr, l, m);
+        mergeSort(arr, m + 1, r);
+
+        merge(arr, l, m, r);
+    }
+}
+
+/* UTILITY FUNCTIONS */
+/* Function to print an array */
+void printArray(int A[], int size)
+{
+    int i;
+    for (i = 0; i < size; i++)
+        printf("%d ", A[i]);
+    printf("\n");
+}
+
+/* Driver code */
+int main()
+{
+    int arr[] = { 12, 11, 13, 5, 6, 7 };
+    int arr_size = sizeof(arr) / sizeof(arr[0]);
+
+    printf("Given array is \n");
+    printArray(arr, arr_size);
+
+    mergeSort(arr, 0, arr_size - 1);
+
+    printf("\nSorted array is \n");
+    printArray(arr, arr_size);
+    return 0;
+}

C/QuickSort.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+
+// function to swap elements
+void swap(int *a, int *b) {
+  int t = *a;
+  *a = *b;
+  *b = t;
+}
+
+// function to find the partition position
+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 the pivot element 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 right 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);
+  }
+}
+
+// function to print array elements
+void printArray(int array[], int size) {
+  for (int i = 0; i < size; ++i) {
+    printf("%d  ", array[i]);
+  }
+  printf("\n");
+}
+
+// main function
+int main() {
+  int data[] = {8, 7, 2, 1, 0, 9, 6};
+
+  int n = sizeof(data) / sizeof(data[0]);
+
+  printf("Unsorted Array\n");
+  printArray(data, n);
+
+  // perform quicksort on data
+  quickSort(data, 0, n - 1);
+
+  printf("Sorted array in ascending order: \n");
+  printArray(data, n);
+}