二叉树的建立与遍历

http://acm.sdut.edu.cn/sdutoj/showproblem.php?pid=2136&cid=1145

#include<stdio.h>   
#include<malloc.h>   
typedef struct node   
{   
    char data ;   
    struct node *l, *r ;   
}tree ;   
tree *t ;   
tree *creat(tree *t)   
{   
    char c ;   
    if((c = getchar())==',')   
    return NULL ;   
    else  
    {   
        t = (tree*)malloc(sizeof(tree)) ;   
        t->data  = c ;   
        t->l = creat(t->l) ;   
        t->r = creat(t->r) ;   
    }   
    return t ;   
}   
void midsearch(tree *t)   
{   
    if(t!=NULL)   
    {   
        midsearch(t->l) ;   
        printf("%c", t->data) ;   
        midsearch(t->r) ;   
    }   
}   
void lastsearch(tree *t)   
{   
    if(t!=NULL)   
    {   
        lastsearch(t->l) ;   
        lastsearch(t->r) ;   
        printf("%c", t->data) ;   
    }   
}   
int leaf(tree *t)   
{   
    if(t==NULL)   
    return 0 ;   
    if(t->l==NULL&&t->r==NULL)   
    return 1 ;   
    else return(leaf(t->l)+leaf(t->r)) ;   
}   
int deep(tree *t)   
{   
    if(t==NULL)   
    return 0 ;   
    int m, n ;   
    m = deep(t->l) ;   
    n = deep(t->r) ;   
    if(m>n)   
    return m+1 ;   
    else return n+1 ;   
}   
int main()   
{   
    tree *p ;   
    int leafs ;   
    p = creat(t) ;   
    midsearch(p) ;   
    puts("") ;   
    lastsearch(p) ;   
    puts("") ;   
    leafs = leaf(p) ;   
    printf("%d\n", leafs) ;   
    printf("%d\n", deep(p)) ;   
    return 0 ;   
}