在字符串中查找子串

#author by changingivan
#2016/04/12 
#include <iostream>
 2 #include <string>
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     //char str1[10], str2[10];
 8     string str1,str2;
 9     cin>>str1;
10     cin>>str2;
11     char *str3,*str4;
12     str3=const_cast<char*>(str1.c_str());
13     str4=const_cast<char*>(str2.c_str());
14     char * p1,* p2,*ini1,*ini2;
15     ini1=p1=str3;
16     ini2=p2=str4;
17     while(ini1!=NULL)
18     {
19         p1=ini1;
20         p2=ini2;
21         while(*p1==*p2 && p1!=NULL&&p1!=NULL)
22         {
23             cout<<*p1<<endl;
24             cout<<*p2<<endl;
25             p1++;
26             p2++;
27         }
28         if(*p2==NULL)
29         {
30 
31             cout<<"finished!"<<endl;
32         }
33         ini1++;
34     }
35 
36     return 0;
37 }