二叉树的建立,以及递归前中后序遍历二叉树

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

#define TREE "+*E*D/CAB"

typedef int dt;
typedef struct NODE {

dt          data;

struct NODE *lp;

struct NODE *rp;

} Node, *Nodep;

void first(Nodep ptr) {
if (ptr) {
printf("%c", ptr->data);
first(ptr->lp);
first(ptr->rp);
}
}

void mid(Nodep ptr) {
if (ptr) {
mid(ptr->lp);
printf("%c",ptr->data);
mid(ptr->rp);
}
}

void last(Nodep ptr) {
if (ptr) {
last(ptr->lp);
last(ptr->rp);
printf("%c", ptr->data);

}

}

int main() {
Nodep   root = NULL;
Nodep   tnode = (Nodep)malloc(sizeof(Node));
Nodep   pl = NULL;
Nodep   pr = NULL;
char s[] = TREE;

//建立二叉树
root = tnode;
tnode->data = s[0];
tnode->lp = NULL;
tnode->rp = NULL;

char *p = s + 1;
while(*p) {
//printf("%c", *p++);
pl = (Nodep)malloc(sizeof(Node));
pl->data = *p++;
pl->lp = NULL;
pl->rp = NULL;

pr = (Nodep)malloc(sizeof(Node));
pr->data = *p++;
pr->lp = NULL;
pr->rp = NULL;

tnode->lp = pl;
tnode->rp = pr;
tnode = tnode->lp;
}

//test
puts("Middle:");
mid(root);
puts("");

puts("First:");
first(root);
puts("");

puts("Last:");
last(root);
puts("");
puts("");

return 0;
}