initial commit

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.12)
+project(sorts C)
+
+set(CMAKE_C_STANDARD 99)
+
+add_executable(sorts main.c sorts.c)
+add_executable(test_sorts test.c sorts.c)

main.c

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+#include <stdio.h>
+#include <time.h>
+#include <bits/time.h>
+#include <stdlib.h>
+#include "sorts.h"
+
+void init_arr(double* arr, size_t n) {
+  for (size_t i = 0; i < n; i++ ){
+    arr[i] = (double) (rand() % (2 << 10)) / 42;
+  }
+}
+
+void do_test(size_t n) {
+  double arr[n];
+  long start = clock() * 1000 / CLOCKS_PER_SEC;
+  long elapsed;
+  size_t sorts = 0;
+  srand(time(0));
+  do {
+    init_arr(arr, n);
+    quicksort(arr, n);
+    elapsed = clock() * 1000 / CLOCKS_PER_SEC - start;
+    sorts++;
+  } while (elapsed < 2500);
+  printf("Quicksort:\n%lu sorts done in %ld ms, avg: %.5f ms\n", sorts, elapsed, (double) elapsed / sorts);
+
+  start = clock() * 1000 / CLOCKS_PER_SEC;
+  sorts = 0;
+  do {
+    init_arr(arr, n);
+    shellsort(arr, n);
+    elapsed = clock() * 1000 / CLOCKS_PER_SEC - start;
+    sorts++;
+  } while (elapsed < 2500);
+  printf("Shellsort:\n%lu sorts done in %ld ms, avg: %.5f ms\n", sorts, elapsed, (double) elapsed / sorts);
+
+  start = clock() * 1000 / CLOCKS_PER_SEC;
+  sorts = 0;
+  do {
+    init_arr(arr, n);
+    selectionsort(arr, n);
+    elapsed = clock() * 1000 / CLOCKS_PER_SEC - start;
+    sorts++;
+  } while (elapsed < 2500);
+  printf("Selection sort:\n%lu sorts done in %ld ms, avg: %.5f ms\n", sorts, elapsed, (double) elapsed / sorts);
+}
+
+int main() {
+  printf("Doing test for n = 2 << 9\n");
+  do_test(2 << 9);
+  printf("\n");
+  printf("Doing test for n = 2 << 12\n");
+  do_test(2 << 12);
+  printf("\n");
+  printf("Doing test for n = 2 << 15\n");
+  do_test(2 << 15);
+  printf("\n");
+}

sorts.c

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+//
+// Created by red on 01/12/19.
+//
+
+#include "sorts.h"
+#include <stdio.h>
+#include <stddef.h>
+
+unsigned long partition(double* arr, unsigned long n) {
+  double pivot = arr[n-1];
+  unsigned long i = 0;
+  for (unsigned long j = 0; j < n-1; j++) {
+    if (arr[j] < pivot) {
+      double tmp = arr[i];
+      arr[i] = arr[j];
+      arr[j] = tmp;
+      i++;
+    }
+  }
+  double tmp = arr[i];
+  arr[i] = arr[n-1];
+  arr[n-1] = tmp;
+  return i;
+}
+
+//quicksort the array pointed at by arr, containing n elements in total.
+void quicksort(double* arr, unsigned long n) {
+  if (n < 2) { return; }
+  unsigned long pivot = partition(arr, n);
+  quicksort(arr, pivot);
+  quicksort(arr+pivot+1, n-pivot-1);
+}
+
+
+//Ciura (2001), A102549
+static size_t const gaps[8] = {701, 301, 132, 57, 23, 10, 4, 1};
+static size_t const gaps_num = 8;
+
+void shellsort(double* arr, size_t n) {
+  //literally the example code from wikipedia i'm lazy
+  for (size_t i = 0; i < gaps_num; i++){
+    size_t gap = gaps[i];
+    for (size_t j = gap; j < n; j++) {
+      double tmp = arr[j];
+      size_t k;
+      for (k = j; k >= gap && arr[k - gap] > tmp; k -= gap) {
+        arr[k] = arr[k-gap];
+      }
+      arr[k] = tmp;
+    }
+  }
+};
+
+
+void selectionsort(double* arr, size_t n) {
+  for (size_t i = 0; i < n; i++) {
+    size_t min = i;
+    for (size_t j = i+1; j < n; j++) {
+      if (arr[j] < arr[min]) {min = j;}
+    }
+    if (min != i) {
+      double tmp = arr[i];
+      arr[i] = arr[min];
+      arr[min] = tmp;
+    }
+  }
+}

sorts.h

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+//
+// Created by red on 01/12/19.
+//
+
+#ifndef SORTS_SORTS_H
+#define SORTS_SORTS_H
+
+#include <stddef.h>
+void quicksort(double* arr, size_t n);
+void shellsort(double* arr, size_t n);
+void selectionsort(double* arr, size_t n);
+
+#endif //SORTS_SORTS_H

test.c

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+//
+// Created by red on 01/12/19.
+//
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include "sorts.h"
+
+void print_elements(double* arr, size_t n) {
+  printf("Elements of array:\n");
+  for (size_t i = 0; i < n; i++) {
+    printf("%.4f ", arr[i]);
+  }
+  printf("\n");
+}
+
+void init_arr(double* arr, size_t n) {
+  for (size_t i = 0; i < n; i++ ){
+    arr[i] = (double) (rand() % (2 << 10)) / 42;
+  }
+}
+
+int main() {
+  srand(time(0));
+  puts("Testing quicksort...");
+  double* arr = calloc(10, sizeof(double));
+  init_arr(arr, 10);
+  print_elements(arr, 10);
+  quicksort(arr, 10);
+  print_elements(arr, 10);
+  puts("Sorted!");
+
+  puts("Testing shellsort...");
+  init_arr(arr, 10);
+  print_elements(arr, 10);
+  shellsort(arr, 10);
+  print_elements(arr, 10);
+  puts("Sorted!");
+
+  puts("Testing selection sort...");
+  init_arr(arr, 10);
+  print_elements(arr, 10);
+  selectionsort(arr, 10);
+  print_elements(arr, 10);
+  puts("Sorted!");
+}