输出不正确。 C ++引物1.4.4 [英] Incorrect output. C++ primer 1.4.4

问题描述

以下程序应该计算用户输入整数的次数。例如：用户输入42 42 10 10.程序应该输出：42发生2次，10发生2次。

the following program is supposed to count the number of times a user inputs a integer. example: user inputs 42 42 10 10. the program is supposed to out put : 42 occurs 2 times, 10 occurs 2 times.

问题：代码不会输出数字10的最后结果，直到您输入另一个数字。我已经粘贴下面的代码。这段代码来自c ++的引文。 1.4.4

the problem: the code will not output the last result for the number 10 until you input another number. i have pasted the code below. this code comes from c++ primer. 1.4.4

#include <iostream>
int main()
{
    // currVal is the number we're counting; we'll read new values into val
    int currVal = 0, val = 0;

    // read first number and ensure that we have data to process
    if (std::cin >> currVal) 
    {
        int cnt = 1;  // store the count for the current value we're processing

        while (std::cin >> val) 
        { // read the remaining numbers

            if (val == currVal)   // if the values are the same
                ++cnt;            // add 1 to cnt
            else 
            { // otherwise, print the count for the previous value
                std::cout << currVal << " occurs " << cnt << " times" << std::endl;
                currVal = val;    // remember the new value
                cnt = 1;          // reset the counter
            }

        }  // while loop ends here

        // remember to print the count for the last value in the file
        std::cout << currVal <<  " occurs " << cnt << " times" << std::endl;
    } // outermost if statement ends here

    return 0;
}

推荐答案

更正由空格分隔的一系列数字输入。

Your program as-written appears correct for a series of numeric inputs separated by whitespace.

您需要向程序提供文件结束指示，以便退出 while 循环并打印最终数据的计数。在Windows中，您可以通过输入[Ctrl] - [Z]作为新行上的第一个字符来实现。在Linux，UNIX和Mac OS X中，[Ctrl] - [D]的作用类似。

You need to give an end-of-file indication to the program so that it will exit the while loop and print the count for the final data. In Windows, you can do that by entering [Ctrl]-[Z] as the first character on a new line. In Linux, UNIX and Mac OS X, [Ctrl]-[D] serves a similar purpose.

或者，您可以将您的值集放入文本文件，使用重定向来喂养您的程序。例如，假设您将数据放在与可执行文件相同的目录中名为 data.txt 的文件中。在终端窗口中，您可以按如下方式运行程序：

Alternately, you can put your set of values into a text file and use redirection to feed your program. Suppose, for example, you put your data in a file named data.txt in the same directory as your executable. In a terminal window, you can run your program as follows:

myprogram < data.txt

如其他人所说，非数字输入也可以代替end的文件。例如，您可以输入 42 42 10 10 fred ，它会输出您期望的结果。这似乎不是程序的意图，但。例如，如果您输入 42 42 10 10 fred 37 ，程序将停止在 fred ，并且不会看到 37

As some others have noted, a non-numeric input will also work in place of end of file. For example, you could enter 42 42 10 10 fred, and it'll output what you expect as well. That doesn't appear to be the intent of the program, though. For example, if you input 42 42 10 10 fred 37, the program stops at fred and won't see 37.

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