我如何获得一个C ++程序来计算用户输入时的单词数？

Question

I'm trying to write a program that keeps taking input from the user until the user enters "quit." Each time the user enters input, I want the program to print out the number of words the user has entered. So the following input on the user's part:

hello how are you

would yield the following output:

You entered 4 words.

However, I am having trouble writing the program so that it counts the number of words on just one line; it doesn't clear the number before going onto the next line. So, if it took input from the user three times, it would add up the total number of words on those three lines. For example, the following input:

how are you
i am good thank you
quit

would yield the following output:

 You entered 9 words.

when I want it to output the number of words following each line the user enters (except quit), ie

>>how are you
<<You entered 3 words.
>>i am good thank you
<<You entered 5 words.
>>quit

Here's the relevant bit of my code:

char *input;
int inum;

int inputLoop()
{
    char quit[] = "quit";
    inum = 0; //counts number of words

    while (strcmp(input, quit) != 0)
    {
         cin >> input;
         inum++;
    }
    cout <<"You entered " <<inum <<" words." <<endl;

I'd rather not use something like a vector; whatever I use will need to be converted to a *char eventually because my global variable is a *char. (And my global variable is a *char because, depending on certain conditions, *input may be set to *argv[] from main.)

I've tried all sorts of things, but I just can't seem to get past the fact that strcmp(input, quit) compares one word of the input at a time to quit rather than comparing the entire input line to quit. HELP.

Answer 1

None of your requirements precludes the use of std::string and std::vector . I recommend you use them.

#include <string>
#include <sstream>
#include <iostream>
#include <vector>

std::vector<std::string> words;

int inputLoop()
{
    char quit[] = "quit";
    total_words = 0;

    std::string line;
    // grab a line at a time
    while(std::getline(std::cin, line) && line != quit) {
        // clear the vector of words
        words.clear();
        // make a string stream to read words from that line
        std::stringstream ss(line);
        // grab all the words into a vector
        std::string word;
        while(ss >> word) {
             words.push_back(word);
        }
        std::cout <<"You entered " <<words.size() <<" words." <<endl;
    }
}

int main(int argc, char** argv) {
    // get the data from argv
    words = std::vector<std::string>(argv, argv + argc);
}

Answer 2

You should use getline() to get an entire line of input into some buffer. Then, process that buffer of input to count the number of words in it. Assuming you define each word to be a block of characters separated by a space. Myself, I am a fan of strtok() for breaking up a buffer.

Answer 3

An alternative approach, just for fun:

#include <iostream>
#include <algorithm>
#include <iterator>

int main()
{
    unsigned num = 0;
    std::for_each(
        std::istream_iterator<std::string>(std::cin),
        std::istream_iterator<std::string>(),

        [&num](const std::string& s)
        {
            if (s == "quit")
                std::cin.setstate(std::ios::eofbit);
            ++num;
            if (std::cin.peek() == '\n') {
                std::cout << "You entered "
                          << num
                          << " word"
                          << ((num == 1) ? "." : "s.")
                          << '\n';
                num = 0;
            }
        });
}

Doesn't waste resources by tokenizing a line into a vector :)

Answer 4

I would call distance

#include <string>
#include <algorithm>
#include <iterator>
#include <iostream>
#include <sstream>

int main()
{
    std::string line;
    while(std::getline(std::cin, line) && line != "quit")
    {
        std::stringstream  linestream(line);
        std::cout << "You entered "
                  << std::distance(std::istream_iterator<std::string>(linestream), 
                                   std::istream_iterator<std::string>())
                  << " words\n";
    }
}