Question

I’ve been looking (without great luck) for the perfect reference card with all the basic sorting algos in C (or maybe in pseudo code). Wikipedia is a terrific source of info but this time I’m looking for something definitely more portable (pocket size if possible) and of course printable. Any suggestion would be much appreciated!

Answer 1

I made this for a friend of mine studying C, maybe you will find it helpful:

#include <stdlib.h> #include <string.h>  static void swap(int *a, int *b) {     if (a != b) {         int c = *a;         *a = *b;         *b = c;     } }  void bubblesort(int *a, int l) {     int i, j;      for (i = l - 2; i >= 0; i--)         for (j = i; j < l - 1 && a[j] > a[j + 1]; j++)             swap(a + j, a + j + 1); }  void selectionsort(int *a, int l) {     int i, j, k;     for (i = 0; i < l; i++) {         for (j = (k = i) + 1; j < l; j++)             if (a[j] < a[k])                 k = j;         swap(a + i, a + k);     } }  static void hsort_helper(int *a, int i, int l) {     int j;      for (j = 2 * i + 1; j < l; i = j, j = 2 * j + 1)         if (a[i] < a[j])             if (j + 1 < l && a[j] < a[j + 1])                 swap(a + i, a + ++j);             else                 swap(a + i, a + j);         else if (j + 1 < l && a[i] < a[j + 1])             swap(a + i, a + ++j);         else             break; }  void heapsort(int *a, int l) {     int i;      for (i = (l - 2) / 2; i >= 0; i--)         hsort_helper(a, i, l);      while (l-- > 0) {         swap(a, a + l);         hsort_helper(a, 0, l);     } }  static void msort_helper(int *a, int *b, int l) {     int i, j, k, m;      switch (l) {         case 1:             a[0] = b[0];         case 0:             return;     }      m = l / 2;     msort_helper(b, a, m);     msort_helper(b + m, a + m, l - m);     for (i = 0, j = 0, k = m; i < l; i++)         a[i] = b[j < m && !(k < l && b[j] > b[k]) ? j++ : k++]; }  void mergesort(int *a, int l) {     int *b;      if (l < 0)         return;      b = malloc(l * sizeof(int));     memcpy(b, a, l * sizeof(int));     msort_helper(a, b, l);     free(b); }  static int pivot(int *a, int l) {     int i, j;      for (i = j = 1; i < l; i++)         if (a[i] <= a[0])             swap(a + i, a + j++);      swap(a, a + j - 1);      return j; }  void quicksort(int *a, int l) {     int m;      if (l <= 1)         return;      m = pivot(a, l);     quicksort(a, m - 1);     quicksort(a + m, l - m); }  struct node {     int value;     struct node *left, *right; };  void btreesort(int *a, int l) {     int i;     struct node *root = NULL, **ptr;      for (i = 0; i < l; i++) {         for (ptr = &root; *ptr;)             ptr = a[i] < (*ptr)->value ? &(*ptr)->left : &(*ptr)->right;         *ptr = malloc(sizeof(struct node));         **ptr = (struct node){.value = a[i]};     }      for (i = 0; i < l; i++) {         struct node *node;         for (ptr = &root; (*ptr)->left; ptr = &(*ptr)->left);         a[i] = (*ptr)->value;         node = (*ptr)->right;         free(*ptr);         (*ptr) = node;     } }