求助：如何用C语言实现字符到数字的映射转换（附代码片段）

Hey there! Let's get your character-to-digit mapping program working correctly. Your original code has a few critical issues (like uninitialized pointers and misusing strcmp for single characters) so we'll fix those and build out the functionality you need.

Key Issues in Your Original Code #

• Uninitialized pointers: char *test; and char *result; are wild pointers—writing to them will cause memory errors. We'll use fixed-size arrays instead.
• Misusing strcmp: strcmp compares entire strings, but you're working with single characters. Just use direct character comparison with == instead.
• Incorrect character assignment: result[i] = "2"; uses a string literal (double quotes), but you need a single character (single quotes: '2').

Fixed & Complete Code #

#include <stdio.h>
#include <string.h>
#include <ctype.h> // For toupper()

int main() {
    // Arrays to store input (max 5 chars + null terminator) and result
    char test[6] = {0};
    char result[6] = {0};
    int char_count = 0;
    int input_char;

    // Read input, limit to 5 alphabetic characters
    while ((input_char = getchar()) != '\n' && char_count < 5) {
        // Only process letters, convert to uppercase for consistent checking
        if (isalpha(input_char)) {
            test[char_count] = toupper(input_char);
            char_count++;
        }
    }
    test[char_count] = '\0'; // Ensure input is a valid C string

    // Map characters to digits based on your rules
    for (int i = 0; i < char_count; i++) {
        if (test[i] == 'A' || test[i] == 'B' || test[i] == 'C') {
            result[i] = '2';
        } else if (test[i] == 'D' || test[i] == 'E' || test[i] == 'F') {
            result[i] = '3';
        }
        // Add more conditions here for other mappings (e.g., G-I → 4, etc.)
        else {
            // Fallback for unrecognized characters (adjust as needed)
            result[i] = '0';
        }
    }
    result[char_count] = '\0'; // Ensure result is a valid C string

    // Print the result
    printf("Input: %s\n", test);
    printf("Output: %s\n", result);

    return 0;
}

How It Works #

• Input Handling: Reads up to 5 alphabetic characters, converts them to uppercase so the mapping works for both lowercase and uppercase inputs.
• Mapping Logic: Directly checks each character against your rules (A-C → 2, D-F → 3). You can easily add more else if blocks to extend the mapping (e.g., G-I to 4, J-L to 5, etc.).
• Memory Safety: Uses fixed-size arrays instead of wild pointers, so you won't run into unexpected memory access errors.
• Test Case Example: If you input AFAF, the program will output 2323—exactly what you requested!

内容的提问来源于stack exchange，提问作者Test