下标的方法：
#include <iostream>
#include <string>
using namespace std;
void replace_(string &s,const string &oldval,const string & newval)
{for(size_t i = 0;i != s.size(); ++ i){if(s[i] == oldval[0]){string temp(s,i,oldval.size());cout << "Temp is:"<< temp << endl;if(temp == oldval){s = s.erase(i,oldval.size());s = s.insert(i,newval);cout << "old i is:" << i << endl;i = i + newval.size() - 1;cout << "new i is :"<<i <<endl << endl;if(i == s.size()){cout << "yes,break it"<<endl << endl;break;}}}}
}
int main()
{ string oldval{"tho"};string s{"asdfasthoasdfthoasdstho"},ss;string newval{"thouth"};replace_(s,oldval,newval);return 0;
}
迭代器的方法：
#include <iostream>
#include <string>
using namespace std;
//replace oldval by newval object to s1
void replace_(string &s1,const string & oldval,const string & newval)
{for(string::iterator it = s1.begin();it != s1.end() ; ++ it){if(*it == *oldval.begin()){string new_str(it,it + oldval.size());if(new_str == oldval){it = s1.erase(it,it+oldval.size());it = s1.insert(it,newval.begin(),newval.end());it += 5; }}} return ;
}
int main()
{string s1 = "asdfasdfthoasdfthoasftho";string oldval = "tho";string newval = "though";unsigned cnt = 1;cout << s1 <<endl;replace_(s1,oldval,newval);cout << s1 <<endl;return 0;
}