翻译句子中单词的顺序

Question

#include <iostream>
#include <cstring>
using namespace std;
void reverse(char* sentence)
{
    int index = strlen(sentence) - 1;
    char last = '\0';
    int hold = 0;
    while ( index != 0){
        while (sentence[index] != ' ')
            index--;
        hold = index; //keeps the index of whitespace
        while (sentence[index] != last){
            cout << sentence[index]; //printing till it either hits end character or whitespace.
            index++;
        }
        last = sentence[hold]; //Keeps the whitespace
        index = hold; //
    }

}
int main()
{
    char* sentence = new char[256];
    cin.getline(sentence, 256);
    reverse(sentence);
}

我想颠倒句子中的单词顺序,你可以看到我的上述尝试.

示例输入和输出应该是这样的:

Howdy Mr. Mcfly? 

Mcfly? Mr. Howdy

我得到的地方:

Howdy Mr. Mcfly?
 Mcfly?

互联网上有许多类似的问题,但我想要的是在我自己的代码中找到错误.

Answer 1

您可以使用std::string std::vector并std::reverse简化操作:

std::string sentence = "Your sentence which contains ten words, two of them numbers";
std::stringstream stream(sentence);
std::vector<std::string> words;
for ( std::string word; stream >> word; )
{
    words.push_back(word);
}

现在你把所有东西分成了单词.您现在可能想要删除问号或其他标点符号,因为在单词仍处于正确顺序时,逻辑将更容易实现.对于倒车,请执行以下操作:

std::reverse(words.begin(), word.end());

您需要包含多个标头:

#include <string> // for storing strings in a C++ way
#include <sstream> // to easily separate sentences into words
#include <vector> // to dynamically store arbitrary amounts of words
#include <algorithm> // for std::reverse

您可以在ideone.com上使用此演示查看此代码

Answer 2

正如其他答案建议您应该使用std::string它可以节省很多麻烦。但只是为了注释，

void reverse(char* sentence)
{
    int index = strlen(sentence) - 1,hold,last = '\0';
    /*For the 1st iteration last is `\0` for all others it is ` `*/
    while (index >= 0)
    {
        /*
        In your original code,
        This while loop(below) will continue to keep decrementing index 
        even below `0`,You wont exit this while loop until you encounter a ` `.
        For the 1st word of the sentence you will never come out of the loop.
        Hence the check, index>=0
        */

        while (index>=0 && sentence[index] != ' ')
        index--;

    /* You can print the whitespace later*/

    hold = index - 1;  // This keeps track of the last character 
                       // of preceding word 

    index++; //character after space

        while (sentence[index] != last)
    {
            cout << sentence[index]; 
            index++;
        }
    last = ' '; 
        index = hold; 

        /* Dont print space after 1st word*/
    if(index > 0)
    cout<<" ";
    }

}
int main()
{
    char* sentence = new char[256];
    cin.getline(sentence, 256);
    reverse(sentence);
    delete[] sentence; // Delete the allocated memory
}

_{尽量让它接近你的逻辑}