在为我的程序抛出一个 'std::out_of_range' 实例后调用 Terminate 来查找和替换字符串中的单词

Question

beginner here, Im getting this error within my program which is supposed to find a word in a string then, replace that word with any that you input. When I input multiple words into the str1, it says this:

terminate called after throwing an instance of 'std::out_of_range'
what(): basic_string::erase:__pos (which is 18446744074709551615) > this->size() (which is 9)

Heres my code:

#include <iostream>
#include <string>

using namespace std;

void findReplace(string& str1,string& str2,string& str3);

int main() 
{
string str1, str2, str3;

cout << "Enter a sentence that you would like to analyze: \n";
cin >> str1;
cin.ignore();
cout << "Enter a word that you would like to search for: \n";
cin >> str2;
cin.ignore();
cout << "Enter a word that would replace the word that was found: \n";
cin >> str3;
cin.ignore();

findReplace(str1,str2,str3);

return 0;
}

void findReplace(string& str1,string& str2,string& str3)
{
  int length= 0;
  int str2len= 0;
  int str3Length = 0;

  length = str1.length();
  str2len = str2.length();
  str3Length = str3.length();
  
  int found = str1.find(str2);

  if ((found!= string::npos))
  {
    cout << str2 << " found at " << found << endl;
  }

  str1.erase(found, str2len);

  str1.replace(found, str3Length, str3 );
  
  cout << str1;

}

Answer 1

The error message contains two big hints: basic_string::erase , the exception was thrown in the call to erase and 18446744074709551615 is maximum 64 bit unsigned in int which on a modern 64 bit system matches the definition of npos

static const size_type npos = -1;

So let's take a look at what lead up to the call to erase :

  int found = str1.find(str2); // find str2

  if ((found!= string::npos))
  { // found str2
    cout << str2 << " found at " << found << endl; // print that we found it
  }

  str1.erase(found, str2len); // erase it (even if we didn't find it)

  str1.replace(found, str3Length, str3 ); // replace it (even if we didn't find it)

Fix:

  auto found = str1.find(str2); // Note: Position ISN'T an int. auto will 
                                // find and use correct type. If auto's not available
                                // size_t will do the job.

  if ((found!= string::npos))
  { // found str2
    cout << str2 << " found at " << found << endl; // print that we found it
    str1.erase(found, str2len); // erase it 

    str1.replace(found, str3Length, str3 ); // replace it 
  }

In addition:

cin >> str1;

will read only one word. Since you need a sentence, use std::getline

You can discard all of the cin.ignore() s. They are useless here. >> will consume any leftover whitespace before the token tit finds. It will leave whitespace after the token, so watch out for Why does std::getline() skip input after a formatted extraction? if you place a std::getline after a >> .