Quicksort and file rearrange

Lab1/quicksort.c

@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+enum PivotStrategy { RIGHTMOST = 0, MIDDLE = 1, RANDOM = 2 };
+
+void swap(int *a, int *b) {
+  int temp = *a;
+  *a = *b;
+  *b = temp;
+}
+
+int partition(int A[], int left, int right, int pivot_strategy, int length) {
+  int pivot_index;
+  if (pivot_strategy == RIGHTMOST) {
+    pivot_index = right;
+  } else if (pivot_strategy == MIDDLE) {
+    pivot_index = (left + right) / 2;
+  } else if (pivot_strategy == RANDOM) {
+    pivot_index = (rand() % (length + 1));
+  }
+
+  int pivot = A[pivot_index];
+  swap(&A[pivot_index], &A[right]);
+  int i = left - 1;
+
+  for (int j = left; j < right; j++) {
+    if (A[j] <= pivot) {
+      i++;
+      swap(&A[i], &A[j]);
+    }
+  }
+  swap(&A[i + 1], &A[right]);
+  return i + 1;
+}
+
+void quicksort(int A[], int p, int r, int pivot_strategy, int length) {
+  if (p < r) {
+    int q = partition(A, p, r, pivot_strategy, length);
+    quicksort(A, p, q - 1, pivot_strategy, length);
+    quicksort(A, q + 1, r, pivot_strategy, length);
+  }
+}
+
+int main() {
+  int size, pivot_strategy;
+
+  if (scanf("%d", &size) != 1) {
+    fprintf(stderr, "Error reading size\n");
+    return 1;
+  }
+
+  if (scanf("%d", &pivot_strategy) != 1) {
+    fprintf(stderr, "Error reading pivot strategy\n");
+    return 1;
+  }
+  // Init the random number generator when needed
+  if (pivot_strategy == RANDOM) {
+    srand(size);
+  }
+
+  int *array = malloc(sizeof(int) * size);
+  if (array == NULL) {
+    fprintf(stderr, "Memory allocation failed\n");
+    return 1;
+  }
+
+  for (int i = 0; i < size; i++) {
+    if (scanf("%d", &array[i]) != 1) {
+      fprintf(stderr, "Error reading array element\n");
+      free(array);
+      return 1;
+    }
+  }
+
+  quicksort(array, 0, size - 1, pivot_strategy, size);
+
+  free(array);
+  return 0;
+}