Binary Tree Traversals and Expression Evaluation in C

Binary Tree Traversals and Expression Evaluation in C

This document contains formatted C code snippets for expression tree evaluation and binary tree traversals (preorder, inorder and postorder). Comments and strings are corrected for clarity while preserving original content.

Expression Tree Evaluation Function

 int evaluate (NodeB n, btree T)
 (
   char ident;

   EtiquetaArbolB (& c, n, T);
   switch (c) (
     case '+':
       return evaluate (HijoIzqdaB (n, T), G) + evaluate (HijoDrchaB (n, T), T);
       break;
     case '-':
       return evaluate (HijoIzqdaB (n, T), T)-Evaluation (HijoDrchaB (n, T), T);
       break;
     case '*':
       return evaluate (HijoIzqdaB (n, T), T) * Evaluation (HijoDrchaB (n, T), T);
       break;
     case '/':
       return evaluate (HijoIzqdaB (n, T), T) / Evaluation (HijoDrchaB (n, T), T);
       break;
     default:
       return value (c);
 

Postorder from Preorder and Inorder

# include <stdio.h>
# include <stdlib.h>
# include <string.h>

char * preorder = "GEAIBMCLDFKJH";
char * inorder = "IABEGLDCFMKHJ";
char * postorder;

/*---------------------------------------*/

void post (char * pre, char * in, char * pos, int n)
(
  int longIzqda;

  if (n> 0) (
    pos [n-1] = pre [0];
    longIzqda = strchr (in, pre [0])-in;
    post (pre +1, in, pos, longIzqda);
    post (pre +1 + longIzqda, in +1 + longIzqda, longIzqda pos + n-1-longIzqda);
  )
)

/*----------------------------------------*/

int main (int argc, char * argv [])
(
  int aux;

  aux = strlen (inorder);
  postorder = (char *) malloc (aux * sizeof (char));
  if (postorder) (
    printf ("Preorder: %s\n", preorder);
    printf ("Inorder: %s\n", inorder);
    post (preorder, inorder, postorder, aux);
    postorder [aux] = '\0';
    printf ("Postorder (calculated): %s\n", postorder);
    free (postorder);
  )
  else (
    fprintf (stderr, "Error: Out of memory\n");
    return 1;
  )

  return 0;
____________________________________

Non-Recursive Inorder Traversal (B-tree)

# include <pilas.h>
# include <arbolesB.h>


/*---------------------------------------*/

void inordenNR (btree T, void (* EscribirElemento) (void *), int size)
(
  NodeB nodoActual, aux;
  void * et;
  Stack p;
  int end;
  faltaHD int / * Indicates whether lack the right child * /

  p = CrearPila (sizeof (NodeB));
  et = malloc (size);
  if (et) (
    .... / * Error: Out of memory * /
  )

  aux = NODOB_NULO;
  Push (& aux, p);
  nodoActual = RaizB (T);
  end = 0;
  while (! end) (
    while (nodoActual! = NODOB_NULO) (
      Push (& nodoActual, p);
      nodoActual = HijoIzqdaB (nodoActual, T);
    )
    Tope (& nodoActual, p);
    Pop (p);
    if (nodoActual! = NODOB_NULO) (
      EtiquetaArbolB (et, nodoActual, T);
      (* EscribirElemento) (et);
      nodoActual = HijoDrchaB (nodoActual, T);
    )
    else order = 1;
  )

  free (et);
  DestruirPila (p);
)

Notes

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