Question

我需要帮助完成课堂任务，基本上我需要从文本文件中读取字母，对每个字母的出现进行计数，并按大多数出现的次数对它们进行排序。我在排序后记住每个字母的原始计数时遇到问题（因为索引更改）问题是结果字母出现的次数多于一次，所以我丢失了一些字母

#include <iostream>
#include <fstream>
#include <string>
#include <stdio.h>    
#include <stdlib.h>    
#include <time.h>

using namespace std;

int main ()
{

    char letter, b[26] = {};
    int number[26] = {0}, temp, i, j;

    ofstream outfile ("test.txt");

    srand (time(NULL));

    for(int i=0;i<20;i++){
        char c = rand() % 26 + 65 + rand() % 2 * 32;
        outfile <<c<<endl;
    }
    outfile.close();

    ifstream file( "test.txt");

    while(file >> letter){

        if (letter >= 'a' && letter <= 'z') number[letter - 'a']++;
        if (letter >= 'A' && letter <= 'Z') number[letter - 'A']++;
    }

    for(i=0; i<26; i++)
    {
        for(j=i+1; j<26; j++)
        {
            if(number[j] > number[i])
            {
                temp = number[i];

                b[i] = char(97+j);

                number[i] = number[j];
                number[j] = temp;
            }
        }
    } 

    for(i=0;i<26;i++){
        if(number[i] != 0)cout<<b[i]<<"  "<<number[i]<<endl;
    }

    return 0;
}

l  3
m  3
m  2
q  2
w  2
j  1
l  1
m  1
o  1
q  1
t  1
v  1
w  1

Answer 1

要扩大我在使用结构的评论中所说的话，请考虑以下问题：

#include <iostream>
#include <fstream>
#include <string>
#include <stdio.h>    
#include <stdlib.h>    
#include <time.h>

using namespace std;

struct CharInstance {
    int count;
    char letter;
};

int main()
{
    char letter;
    int i, j;
    CharInstance temp;
    CharInstance charInst[26] = { 0 };

    // create test data randomly
    {
        ofstream outfile("test.txt");

        srand(time(NULL));

        for (int i = 0; i < 500; i++) {
            char c = rand() % 26 + 65 + rand() % 2 * 32;
            outfile << c << endl;
        }
        outfile.close();
    }

    // read in data and store in array
    {
        ifstream file("test.txt");
        while (file >> letter) {
            // force lowercase to uppercase so we count both lowercase and uppercase as the same
            if (letter >= 'a' && letter <= 'z') letter -= 32;
            // since all input is now uppercase, ignore anything that isn't in uppercase range
            if (letter < 'A' || letter > 'Z') continue; // skip non-alpha chars

            const int ind = letter - 'A';
            ++charInst[ind].count;
            charInst[ind].letter = letter;
        }
        file.close();
    }

    // bubble sort
    for (i = 0; i < 26; i++)
    {
        for (j = i + 1; j < 26; j++)
        {
            if (charInst[j].count > charInst[i].count)
            {
                temp = charInst[i];
                charInst[i] = charInst[j];
                charInst[j] = temp;
            }
        }
    }

    for (i = 0; i < 26; i++) {
        cout << charInst[i].letter << ": " << charInst[i].count << "  " << endl;
    }

    return 0;
}

Answer 2

如果您不介意C ++ 11。

#include <fstream>
#include <iostream>
#include <map>
#include <vector>

int main() {
  std::ifstream in("sort.cpp");

  // Map to store counts of each character.
  // Note: this won't work with some international characters (i.e. Chinese).
  std::map<char, int> histogram; 



  char ch = 0;
  while (in.get(ch)) {
    // TODO
    // Filter out characters you don't want, as this would also pick whitespaces
    // and newlines.

    // Increment the count for |ch|.
    // This would create new map element if the count was zero.
    ++histogram[ch];
  }

  // Move map contents into an array of pairs character->count.
  std::vector<std::pair<char, int>> pairs(histogram.begin(), histogram.end()); 

  // Sort the array. The third parameter is a function used as a custom comparator.
  std::sort(pairs.begin(), pairs.end(),
      [](const std::pair<char, int>& left, const std::pair<char, int>& right) {
        // Use the count to compare |left| and |right|.
        return left.second > right.second;
      });

  for (const auto& pair : pairs) {
    std::cout << pair.first << " " << pair.second << std::endl;
  }
}


g++ -std=c++11 sort.cpp 
./a.out

  207
t 79
a 62
e 61
r 61
i 53
s 51
o 50
n 50
c 46
...

C ++从文件中读取字符，对每个字符进行计数并排序

2 个答案: