#include<iostream>
using namespace std;
int index(char *s,char *t)
{
    int i=0;
    int j=0;
    while(s[i]!='\0')
    {
        if(s[i]==t[j])
        {
            i++;
            j++;
        }
        else
        {
            i++;
            j=0;
            continue;
        }
        if(t[j]=='\0')
            return i-j;
    }
    return -1;
}
void main()
{
    char a[]="abcdefg";      //这行写成这样运行没错， 如果把char a[]="abceddefg"改为这样， 运行时就出错！！这什么原因啊 请大家帮帮忙啊
    char b[]="de";
    int i=index(a,b);
    if(i==-1)
        throw "无匹配子集";
    cout<<"在a["<<i<<"]处开始找到b"<<endl;
    
}