Exer09_28.cpp

#include <iostream>
#include <forward_list>
#include <string>
using std::cout;
using std::endl;
using std::forward_list;
using std::string;
forward_list<string>::iterator insert_word(forward_list<string>& flst, const string& str1, const string& str2)
{
    auto prev = flst.before_begin();
    auto curr = flst.begin();
    while(curr != flst.end())
    {
        if(*curr == str1)
        {
            curr = flst.insert_after(curr, str2);
            return curr;
        }
        else
        {
            prev = curr;
            ++curr;
        }
    }
    curr = flst.insert_after(prev, str2);
    return curr;
}
int main()
{
    forward_list<string> flst = { "The", "wrinkled", "sea", "beneath", "him", "crawls;\n",
                                  "He", "from", "his", "mountain", "walls,\n",
                                  "And", "like", "a", "thunderbolt", "he", "falls.\n" };
    string word1 = "He", word2 = "watches";
    insert_word(flst, word1, word2);
    for(const auto &s : flst)
        cout << s << " ";
    cout << endl;
    return 0;
}