字符串中的反词

Question

This code here is for reversing words in a string. The problem is that it only reverses the first word in the string. When I ran a trace I found that it is stopping after encountering the statement if(s[indexCount] == '\\0') break;

Why the code is getting null character every time the first word is reversed even though some other character is present after the first word.

#include <iostream>
using namespace std;
int main()
{
    string s;
    char tchar;
    int indexCount=0,charCount=0,wordIndex;
    cin>>s;
    while(1){
        if(s[indexCount]==' ' && charCount==0) continue;
        if(s[indexCount]==' ' || s[indexCount]=='\0' ){
            wordIndex=indexCount-charCount;
            charCount=indexCount-1;
            while(charCount!=wordIndex && charCount>wordIndex){
                tchar=s[wordIndex];
                s[wordIndex]=s[charCount];
                s[charCount]=tchar;
                charCount--;
                wordIndex++;
            }
            if(s[indexCount] == '\0') break;
            indexCount++; charCount=0;
        }
        else{
            charCount++;
            indexCount++;
        }
    }
    cout<<"\nReveresed words in the string : \n\t"<<s<<endl;
   return 0;
}

Also I'm using while(1) . Does it make this a bad code?

Answer 1

The problem indeed lies with the method of input. cin >> string_variable will consider whitespace to be a delimiter. That is why only the first word is being entered. Replace cin >> s; with getline(cin, s); and it will work correctly.

Answer 2

First of all I want to point out that

cin >> stringObject;

will never ever read space character! so inserting My name is geeksoul will cause above code to read only My and leave everything else in the buffer!

To read space character you should use getline function like this

std::getline(std::cin, stringObject);

read about getline

Second The standard doesn't say that in case of an std::string '\\0' is any special character. Therefore, any compliant implementation of std::string should not treat '\\0' as any special character. Unless of course a const char* is passed to a member function of a string, which is assumed to be null-terminated. The standard doesn't say that in case of an std::string '\\0' is any special character. Therefore, any compliant implementation of std::string should not treat '\\0' as any special character. Unless of course a const char* is passed to a member function of a string, which is assumed to be null-terminated.

If you really want to check your string with null terminating character then you should consider using stringObject.c_str() which converts your C++ style string to old school C style string!

Check this for c_str

Finally this might be helpful for you!

Answer 3

Quick tip. If you reverse all characters in the whole strings, and then all characters between each pair of consecutive spaces, you will achieve the same result, with way simple code, like this: (Note, this may not compile or be slightly buggy (haven't compiled or anything), but should convey the basic idea)

void reverseWords(std::string& aString) {
    std::reverse(aString.begin(), aString.end());
    size_t lastSpaceIndex = 0;
    for (size_t index = 0; index != aString.size(); ++index) {
        if (aString[index] == ' ') {
             std::reverse(aString.begin() + lastSpaceIndex + 1, aString.begin() + index);
             lastSpaceIndex = index;
        }
    }
}