使用C++统计文本中字母出现次数及占比的技术实现问询

Hey there! Let's build a C++ program that counts how often each letter appears in a given text, calculates their percentage of the total letters, and finds the most frequent one. I'll walk you through the whole process with a clear example.

Here's the plan we'll follow:

• Normalize the text: Convert all letters to uppercase (or lowercase) so we count 'I' and 'i' as the same letter.
• Count occurrences: Use an array of size 26 (one for each letter A-Z) to keep track of how many times each letter appears.
• Calculate total letters: Sum up all valid letter counts to get the total number of letters in the text.
• Compute percentages: For each letter, divide its count by the total letters (as a floating-point number) to get the percentage.
• Find the most frequent letter: Iterate through our count array to find which letter has the highest count.

#include <iostream>
#include <string>
#include <cctype> // For toupper() function

using namespace std;

int main() {
    // Initialize an array to hold counts for A-Z (index 0 = A, 1 = B, ..., 25 = Z)
    int letterCounts[26] = {0};
    string inputText;
    int totalLetters = 0;

    // Get input text from the user
    cout << "Enter the text to analyze: ";
    getline(cin, inputText);

    // Iterate through each character in the text
    for (char c : inputText) {
        // Check if the character is a letter
        if (isalpha(c)) {
            // Convert to uppercase to normalize
            char upperC = toupper(c);
            // Calculate the index in the array (A = 65 in ASCII, so subtract 65)
            int index = upperC - 'A';
            letterCounts[index]++;
            totalLetters++;
        }
    }

    // Check if there are any letters in the input
    if (totalLetters == 0) {
        cout << "No letters found in the input text." << endl;
        return 0;
    }

    // Display the count and percentage for each letter that appears
    cout << "\nLetter Frequency Analysis:\n";
    for (int i = 0; i < 26; i++) {
        if (letterCounts[i] > 0) {
            char letter = 'A' + i;
            double percentage = (static_cast<double>(letterCounts[i]) / totalLetters) * 100;
            cout << "Letter " << letter << ": " << letterCounts[i] << " times (" << percentage << "%)\n";
        }
    }

    // Find the most frequent letter
    int maxCount = 0;
    char mostFrequentLetter = ' ';
    for (int i = 0; i < 26; i++) {
        if (letterCounts[i] > maxCount) {
            maxCount = letterCounts[i];
            mostFrequentLetter = 'A' + i;
        }
    }

    // Display the most frequent letter
    cout << "\nThe most frequent letter is: " << mostFrequentLetter << " (appeared " << maxCount << " times)\n";

    return 0;
}

Let's break down what each part does:

• Normalization: We use toupper() from <cctype> to convert every letter to uppercase. This ensures we don't count 'a' and 'A' separately.
• Counting: The letterCounts array indexes correspond to each letter (0 = A, 1 = B, etc.). For each valid letter, we calculate its index by subtracting the ASCII value of 'A' from the uppercase character, then increment that index's count.
• Total Letters: Every time we count a letter, we increment totalLetters—this lets us calculate accurate percentages later.
• Percentage Calculation: We cast the count to a double before dividing by totalLetters to avoid integer division, then multiply by 100 to get a percentage.
• Finding Most Frequent: We loop through the letterCounts array to track which index has the highest value, then convert that index back to a letter.

If you input the sentence I stay in Ohio, here's what the program will output:

Enter the text to analyze: I stay in Ohio

Letter Frequency Analysis:
Letter A: 1 times (9.09091%)
Letter H: 1 times (9.09091%)
Letter I: 3 times (27.2727%)
Letter N: 1 times (9.09091%)
Letter O: 2 times (18.1818%)
Letter S: 1 times (9.09091%)
Letter T: 1 times (9.09091%)
Letter Y: 1 times (9.09091%)

The most frequent letter is: I (appeared 3 times)

内容的提问来源于stack exchange，提问作者Yahaya Ibrahim