循环的矢量迭代器不可递增In

好吧，我知道人们一直在谈论这个话题，但我已经搜索了一个又一个问题，并反复编辑了我的代码，我似乎仍然有这个问题。这段代码的主要目的是运行一个向量并比较/组合其内容。为了做到这一点，我使用"it"answers"In"来遍历向量，并使用.erase来删除已组合到向量的新部分中的内容。我知道我基本上需要.erase函数和迭代器，所以我使用了StackOverflow上其他问题中的一些代码（auto-it的东西），这些代码似乎在这种情况下有效。由于我不熟悉那个代码，所以我可能在这种情况下错误地使用了它，尽管我对此不确定。

无论如何，正如标题所示，我得到了一个"vector迭代器不可增加"的错误。程序在第二个for循环中运行了几次后，似乎遇到了这个错误。我已经尝试了很多方法，但我似乎无法弄清楚代码的哪一部分才是真正的问题。

如有任何帮助，我们将不胜感激！

if (!strvector.empty()) {
        for (auto in = strvector.begin(); in != strvector.end() - 1;) {//in order to process if there is more than one final piece
            str = ' ' + *in + ' ';//adds spaces so it only compares beginnings & ends
            if (strvector.size() < 2) {
                break;
            }//doesn't do anything if there are too few objects to process
            for (auto it = strvector.begin(); it != strvector.end() - 1;) { 
                if (strvector.size() < 2) {
                    break;
                }//doesn't continue if there are too few objects to process
                str2 = ' ' + *it + ' '; //adds spaces so it only compares beginnings & ends
                substr = str; //sets substring of string to be chopped up
                while (substr.length() >= 6) { //only processes substrings >= 6 characters bc smaller bits are useless
                    size_t found = str2.find(substr); //searches str2 for substr
                    if (found != string::npos) {
                        str = str.substr(0, substr.length()) + ' '; //cuts substr off of str
                        str.append(str2); //adds str and str2
                        it = strvector.erase(it);
                        substr = 'a'; //shortens substr to get out of while
                        test=1;
                    }//end if
                    else {
                        substr.erase(substr.size() - 1, 1); //if substr was not found, decrement substr and compare again
                    }
                }//end while
                substr = str; //resets substr
                while (substr.length() >= 6) { //only processes substrings >= 6 characters bc smaller bits are useless
                    size_t found = str2.find(substr); //searches str2 for substr
                    if (found != string::npos) {
                        str = str.substr(substr.length()) + ' '; //cuts substr from beginning of string
                        str = str2 + str; //adds str2 and str, with str2 at the beginning
                        it = strvector.erase(it++);
                        substr = 'a'; //shortens substr to get out of while 
                        test=1;
                    }//end if
                    else {
                        substr.erase(0, 1); //erases the first character of the string
                    }
                    if (test < 1) {
                        it++; //increments if the erase function did not already do that
                    }
                }//end while
                if (test != 1) {
                    it++; //increments if the erase function did not already do that
                }
                if (test < 2) {
                    strvector.push_back(str); //adds new str to the vector
                    test = 0;
                }
            }//end ptr2 for
            if (strvector.size() < 2) {
                in = strvector.erase(in - 1);
            }
            else {
                in++;
            }
            cout << "str1 is " << str << endl; //prints out str
        }//end ptr for
    }//end if vector is not empty