在C++程序中输入的文本文件将不起作用，除非文本被复制和粘贴

我的代码中有一个非常奇怪的错误，有点难以解释。让我从程序的作用开始：基本上，C++程序获取输入文本(来自同一目录中名为"input.txt"的文件)，并使用马尔可夫链生成一些类似于输入文本样式的人工输出文本，并将其打印到终端。

当我复制并粘贴《爱丽丝梦游仙境》的文本时，它就起作用了(http://paulo-jorente.de/text/alice_oz.txt)直接输入到"input.txt"中，但如果我在文本文件内容的开头或结尾添加任何单词或字符，则代码将停止运行(或无限运行)。但是，如果在文本文件内容中间的任何位置添加文本，则不会发生这种情况。

如果你想自己测试，试着用复制到"input.txt"中的爱丽丝梦游仙境运行代码。然后在成功运行后，转到input.txt，在"爱丽丝"的最后一段文本后键入一些随机字符或单词("…又回家了！")，然后试着再次运行；它将失败。

这是代码：

#include <ctime>
#include <iostream>
#include <algorithm>
#include <fstream>
#include <string>
#include <vector>
#include <map>
using namespace std;
class markovTweet{
string fileText;
map<string, vector<string> > dictionary;
public:
void create(unsigned int keyLength, unsigned int words) {
ifstream f("input.txt");
if(f.good()){
fileText.assign((istreambuf_iterator<char>(f)), istreambuf_iterator<char>());
}else{
cout << "File cannot be read. Ensure there is a file called input.txt in this directory." << "n" << endl;
return;
}
if(fileText.length() < 1){
return;
}
cout << "n" << "file imported" << "n";
createDictionary(keyLength);
cout << "n" << "createDictionary" << "n" << "n";
createText(words - keyLength);
cout << "n" << "text created, done" << endl;
}
private:
void createText(int w) {
string key, first, second;
size_t next;
map<string, vector<string> >::iterator it = dictionary.begin();
advance( it, rand() % dictionary.size() );
key = (*it).first;
cout << key;
while(true) {
vector<string> d = dictionary[key];
if(d.size() < 1) break;
second = d[rand() % d.size()];
if(second.length() < 1) break;
cout << " " << second;
if(--w < 0) break;
next = key.find_first_of( 32, 0 );
first = key.substr( next + 1 );
key = first + " " + second;
}
cout << "n";
}
void createDictionary(unsigned int kl) {
string w1, key;
size_t wc = 0, pos, next;
next = fileText.find_first_not_of( 32, 0 );
if(next == string::npos) return;
while(wc < kl) {
pos = fileText.find_first_of(' ', next);
w1 = fileText.substr(next, pos - next);
key += w1 + " ";
next = fileText.find_first_not_of(32, pos + 1);
if(next == string::npos) return;
wc++;
}
key = key.substr(0, key.size() - 1);
while(true) {
next = fileText.find_first_not_of(32, pos + 1);
if(next == string::npos) return;
pos = fileText.find_first_of(32, next);
w1 = fileText.substr(next, pos - next);
if(w1.size() < 1) break;
if(find( dictionary[key].begin(), dictionary[key].end(), w1) == dictionary[key].end() ) 
dictionary[key].push_back(w1);
key = key.substr(key.find_first_of(32) + 1) + " " + w1;
}
}
};
int main() {  
markovTweet t;
cout << "n" << "Artificially generated tweet using Markov Chains based off of input.txt: " << "n" << "n";
//lower first number is more random sounding text, second number is how long output is.
t.create(4, 30);
return 0;
}

这是一个非常奇怪的错误，非常感谢您能提供的任何帮助！谢谢