Question

cout << "If you would like to find/replace or copy/paste, enter find or copy: " << endl;  
cin >> answer;    
cin.ignore();   
if(answer == "find"){   
  cout << "Enter substring to find: " << endl;   
  cin >> userInput2;   
  cin.ignore();   
  cout << "Do you want to find if/where the substring occurs, delete it, or replace it (find, delete, replace)? " << endl;   
  cin >> answer;   
  cin.ignore();   
  position = userInput.find(userInput2);  
  if(answer == "find"){  
     if(userInput.at(position) == string::npos){
        cout << userInput2 << " was not found.";  
     }else{  
        cout << userInput2 << " was found at position "<< position << "." << endl;
     }

我认为错误可能就在这里：

position = userInput.find(userInput2);  
if(answer == "find"){  
 if(userInput.at(position) == string::npos){
    cout << userInput2 << " was not found.";  
 }else{  
    cout << userInput2 << " was found at position "<< position << "." << endl;
 }

找到答案，找到并输入userInput 2是起司，应该返回userInput was not found或cheese was not found，但我得到的是：

terminate called after throwing an instance of 'std::out_of_range'
what():  basic_string::at: __n (which is 18446744073709551615) >= this->size() (which is 14)

帮助我知道我做错了。

Answer 1

userInput.at(position) == string::npos

不会执行您想要的操作，因为如果position已经是string::npos，则您是在要求string::at从无效位置获取字符。如果您阅读了已提供给我们的错误消息，则可以看到它说明了这一事实：您正在将一个超出范围的疯狂值传递给at，该值显然比您的长度大字符串。

您还应该阅读string::find（有些here）的文档，其中明确指出如果找不到这样的子字符串，该函数将返回npos。

尝试做

if(position == string::npos){

相反。

我的问题是我得到了超出范围的错误

1 个答案: