不等长字符串替换怎么做呀？
void fun(char *str,char *t1,char *t2)
要求把串str中的所有t1替换成t2;注：t1,t2长度不一样。

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#include <stdlib.h>
struct strch{
    char ch;
    struct strch *next;
};


struct strch * creat()
{
    struct strch *head,*p1,*p2;
    int strl=0;
    int n=0;
    head=NULL;
    p1=p2=(struct strch*)malloc(sizeof(struct strch));
    printf("please enter the strch:");
    scanf("%c",&p1->ch);
    while((*p1).ch!='#')
    {
        n=n+1;
        if(head==NULL)head=p1;
        else
            p2->next=p1;
        p2=p1;
            p1=(struct strch*)malloc(sizeof(struct strch));
            scanf("%c",&p1->ch);
    }
    p2->next=NULL;
    return head;
}

void print(struct strch * head)
{
    struct strch *p1;
    p1=head;
    if(p1==NULL)
        printf("this is a null");
    else
        while(p1->next!=NULL)
        {
        printf("%c",(*p1).ch);
        p1=p1->next;
        }
}

void fun(struct strch *&head,struct strch *t1,struct strch *t2)//用t2替换链表（以head为头结点）中的t1
//[bo][size=5这个函数好像没起作用？？？[/size][/bo]
{
    struct strch *p1,*p;
    struct strch *headt1,*headt2;
    headt1=t1;headt2=t2;
    p1=head;
    int i=0;
    if(head==NULL) {printf("none exsit");exit(0);}
    else while(p1->next!=NULL)
    {
        if(p1->ch==t1->ch)
        {
            p=p1;
            for(;p1->ch==t1->ch;p1=p1->next,t1=t1->next);//循环判断head中是否有t1
            if(t1->next==NULL)//如果经上循环t1已经指向未，则说明head中有t1,并已用p标记了t1在head 中出现的起始
            {
                p->next=headt2;
                while(t2->next!=NULL)t2=t2->next;
                t2->next=p1;
                t2=headt2;//当链表中有多个t1时，要保证让t1,t2指向表头
                t1=headt1;
            }
        }
        else p1=p1->next;
    }
}

void main()
{
    struct strch *head,*t1,*t2;
    printf("产生长串");
    head=creat();
    printf("产生长串中的一个子串");
    t1=creat();
    printf("产生替代子串的另一个串");
    t2=creat();
    fun(head,t1,t2);
    print(head);
}

如果要替换多个同样的单词呢？感觉好像用链表还是要好些。上面的程序错哪了呢？