c++ - 我想从一个字符串句子中取出单词并在 C++ 中得到这个错误

Question

#include<iostream>
#include<string>
using namespace std;

void extractFirstWord(string& sentence, string& word);
void processBlanks(string& sentence);

int main() {
    string sentence, word;
    cout << "Input a sentence: ";
    getline(cin, sentence);

    while (sentence != "") {
          processBlanks(sentence); // removes all blanks from the front of sentence
          if (sentence.length() > 0) { // removing blanks may have made sentence null - cannot extract from a null string
             extractFirstWord(sentence, word); // gets first word from sentence and puts into word
             cout << word << endl; // output one word at a time
          }
    }

    system("PAUSE");
    return 0;
}

void extractFirstWord(string& sentence, string& word)
    {
        int i=0;
        while(sentence[i]!=' ')
        {
            i++;        
        }
        word=sentence.substr(0,i);
        sentence=sentence.substr(i);
}
// extractFirstWord removes the substring of sentence 
// from the beginning to the first space from sentence 
// and stores the same string into word. sentence is
// shortened accordingly.
// Postcondition: sentence is shortened, and word
//                is appropriately the first word in
//                sentence.

void processBlanks(string& sentence)
    {
        int i=0;
        while(sentence[i]==' '){i++;}
        sentence=sentence.substr(i);
    }

processBlanks 将删除句子前面的所有空格。后置条件:句子第一个词前没有空格。

我想从一个字符串句子中取出单词并在c++中得到这个错误

错误是 -> 字符串下标超出范围

Answer 1

在 extractFirstWord 中，如果您还没有找到空格，您会不断增加 i。但是，如果它是字符串中的最后一个单词，您可能会索引到字符串的末尾。像这样更改 while 条件:

while(i < sentence.length() && sentence[i]!=' ')