计算文本文件中每个词的出现次数 [英] Counting Occurrences of Each Word in a Text File

问题描述

给定一个具有多个字符串的大型文本文件，什么是最有效的方式来读取文本文件和计数每个单词的出现次数有C ++？文本文件的大小是未知的，所以我不能只使用一个简单的数组。此外，还有另一个catch。此文本文件的每一行以类别关键字开头，后面的单词是该类别的特征。我需要能够计算每个单词在该类别中的出现次数。

Given a large text file with multiple strings, what would be the most efficient way to read the text file and count how many occurrences of each word are there in C++? The text file's size is unknown so I cannot just use a simple array. Also, there is another catch. Each line of this text file starts with a category key word and the following words are the features of that category. I need to be able to count how many occurrences of each word is in that category.

例如：

colors red blue green yellow orange purple
sky blue high clouds air empty vast big
ocean wet water aquatic blue
colors brown black blue white blue blue

$在此示例中，我需要计数颜色类别中出现的四个蓝色，即使

With this example, I need to count that within the "colors" category, there are 4 occurrences of "blue", even though there are 6 total occurrences of blue in total.

推荐答案

我会使用 stream 用于读取和分离单词（通过查找空格分隔单词），并将它们保存到字典（标准C ++方法是使用 std :: map ）。

I would use a stream for reading and separating the words (it separates words by looking for whitespace) and save them to a dictionary (The standard C++ method is to use std::map).

这里是一个C ++记录的代码：

Here is a C++ documented code:

#include <iostream>
#include <map> // A map will be used to count the words.
#include <fstream> // Will be used to read from a file.
#include <string> // The map's key value.
using namespace std;


//Will be used to print the map later.
template <class KTy, class Ty>
void PrintMap(map<KTy, Ty> map)
{
    typedef std::map<KTy, Ty>::iterator iterator;
    for (iterator p = map.begin(); p != map.end(); p++)
        cout << p->first << ": " << p->second << endl;
}

int main(void)
{
    static const char* fileName = "C:\\MyFile.txt";

    // Will store the word and count.
    map<string, unsigned int> wordsCount;


    {
        // Begin reading from file:
        ifstream fileStream(fileName);

        // Check if we've opened the file (as we should have).
        if (fileStream.is_open())
            while (fileStream.good())
            {
                // Store the next word in the file in a local variable.
                string word;
                fileStream >> word;

                //Look if it's already there.
                if (wordsCount.find(word) == wordsCount.end()) // Then we've encountered the word for a first time.
                    wordsCount[word] = 1; // Initialize it to 1.
                else // Then we've already seen it before..
                    wordsCount[word]++; // Just increment it.
            }
        else  // We couldn't open the file. Report the error in the error stream.
        {
            cerr << "Couldn't open the file." << endl;
            return EXIT_FAILURE;
        }

        // Print the words map.
        PrintMap(wordsCount);
    }

    return EXIT_SUCCESS;
}

输出：

空气：1

aquatic：1

big：1

black：1

blue ：6

brown：1

clouds：1

colors：2

empty：1

绿色：1

高位：1

海洋：1

橙色：1

紫色： 1

red：1

sky：1

vast：1

水：1

wet：1

white：1

yellow：1

air: 1
aquatic: 1
big: 1
black: 1
blue: 6
brown: 1
clouds: 1
colors: 2
empty: 1
green: 1
high: 1
ocean: 1
orange: 1
purple: 1
red: 1
sky: 1
vast: 1
water: 1
wet: 1
white: 1
yellow: 1

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