practical of programming 第二章 树

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

typedef struct Nameval Nameval;
struct Nameval{
char *name;
int value;
Nameval *left;  /* lesser */
Nameval *right;  /* greater */
};

/* insert: insert newp in treep, return treep */
Nameval *insert(Nameval *treep, Nameval *newp){
int cmp;
if (treep == NULL)
return newp;
cmp = strcmp(newp->name, treep->name);
if (cmp == 0)
printf("Insert: duplicate entry %s ignored",
newp->name);
else if (cmp<0)
treep->left = insert(treep->left, newp);
else
treep->right = insert(treep->right, newp);
return treep;
}

/* lookup: look up name in tree treep */
Nameval *lookup(Nameval *treep, char *name){
int cmp;
if (treep == NULL)
return NULL;
cmp = strcmp(name, treep->name);
if(cmp==0)
return treep;
else if (cmp < 0)
return lookup(treep->left, name);
else
return lookup(treep->right, name);
}

/* applyinorder: inorder application of fn to treep */
void applyinorder(Nameval *treep,
void (*fn)(Nameval*, void*),void *arg){
if (treep == NULL)
return ;
applyinorder(treep->left,fn,arg);
(*fn)(treep,arg);
applyinorder(treep->right, fn, arg);
}

/* applypostorder: postorder application of fn to treep */
void applypostorder(Nameval *treep,
void(*fn)(Nameval*,void*),void *arg){
if (treep == NULL)
return;
applypostorder(treep->left,fn,arg);
applypostorder(treep->right,fn,arg);
(*fn)(treep,arg);
}