数据结构，使用先序，建立二叉树，错哪里了

Question

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct tree {
struct tree*lchild,*rchild;
char date;
} tree,*ntree;
char ch[100];
int i=0;
int creat(ntree p) {
while(i<=strlen(ch)) {

    if(p->date=='#') return 0;
    else {
        p->date=ch[i];
        creat(p->lchild);
        creat(p->rchild);
    }
    i++;
    p=(ntree)malloc(sizeof(tree));
}

}
int main() {
gets(ch);
ntree p,head;
p=head=(ntree)malloc(sizeof(tree));
if(p) {
printf("初始化成功");
creat(p);
}
}

Answer 1

修改如下，供参考：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct tree {
    struct tree*lchild,*rchild;
    char date;
} tree,*ntree;
char ch[100];
int i=0;
int creat(ntree& p) {
    //while(i<=strlen(ch)) {
    char c = ch[i++];
    if (c == '#' || c == '\0') p = NULL; //if(p->date=='#') return 0;
    else {
          p=(ntree)malloc(sizeof(tree));
          p->date=c;
          creat(p->lchild);
          creat(p->rchild);
    }
    //i++;
    //p=(ntree)malloc(sizeof(tree));
    //}
}
void firstprint(ntree p)
{
    if(p){
        printf("%4c",p->date);
        firstprint(p->lchild);
        firstprint(p->rchild);
    }
}
int main() {
    gets(ch);
    ntree p,head;
    //p=head=(ntree)malloc(sizeof(tree));
    //if(p) {
    //      printf("初始化成功");
    creat(p);
    //}
    firstprint(p);
    
    return 0;
}