二叉樹sdutoj1303

http://acm.sdut.edu.cn/sdutoj/showproblem.php?pid=2137&cid=1303

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct node
{
    char c;
    struct node *r,*l;
};
struct node* xianb(struct node *tree)//先序建樹
{
    char ch;
    scanf("%c",&ch);
    if(ch==',')tree=NULL;
    else{
        tree=(struct node *)malloc(sizeof(struct node));
        tree->c=ch;
        tree->l=xianb(tree->l);
        tree->r=xianb(tree->r);
    }
    return tree;
}
void putzhong(struct node *tree)
{
    if(tree!=NULL)
    {
        putzhong(tree->l);
        printf("%c",tree->c);
        putzhong(tree->r);
    }
}
void puthou(struct node *tree)
{
    if(tree!=NULL)
    {
        puthou(tree->l);
        puthou(tree->r);
        printf("%c",tree->c);
    }
}
int sum;
void ye(struct node *tree)//求葉子個數
{
    if(tree==NULL)return ;
    if(tree->l==NULL&&tree->r==NULL)
    {
        sum++;
    }
    ye(tree->l);
    ye(tree->r);
}
int depth(struct node*tree)//求深度
{
    int dr,dl;
    if(tree==NULL)return 0;
    else
    {
        dl=depth(tree->l);
        dr=depth(tree->r);
        return (dl>dr?dl:dr)+1;
    }
}
int main()
{
    struct node *tree;
    tree=xianb(tree);//有tree未定義的警告，但代碼是對的，警告可忽略
    putzhong(tree);
    printf("\n");
    puthou(tree);
    printf("\n");
    sum=0;
    ye(tree);
    printf("%d\n",sum);
    printf("%d\n",depth(tree));
    return 0;
}