C语言编写一个算法统计在输入字符串中各个不同字符出现的频度，并将结果输出(字符串中的合法字符为a-z、A-Z之间的26个字母和0-9之间的10个数字)。

在C语言中，我们可以创建一个简单的程序来实现这个功能，利用哈希表（例如数组或结构体）存储每个字符及其出现次数。下面是一个基本的实现步骤：

#include <stdio.h>
#include <string.h>

#define ALPHABET_SIZE 26
#define DIGITS_SIZE 10

typedef struct {
    char ch;
    int count;
} Frequency;

void computeFrequency(const char *str, Frequency freqs[ALPHABET_SIZE + DIGITS_SIZE]) {
    for (int i = 0; str[i] != '\0'; ++i) {
        if ('a' <= str[i] && str[i] <= 'z') {
            freqs[str[i] - 'a'].count++;
        } else if ('A' <= str[i] && str[i] <= 'Z') {
            freqs[str[i] - 'A'].count++;
        } else if ('0' <= str[i] && str[i] <= '9') {
            freqs[str[i] - '0'].count++;
        }
    }
}

void printFrequency(Frequency freqs[], int size) {
    printf("Character\tFrequency\n");
    for (int i = 0; i < size; ++i) {
        if (freqs[i].count > 0) {
            printf("%c\t%d\n", freqs[i].ch, freqs[i].count);
        }
    }
}

int main() {
    char input[100];
    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);
    input[strcspn(input, "\n")] = '\0'; // Remove newline character from the end of the input

    Frequency freqs[ALPHABET_SIZE + DIGITS_SIZE] = {0};
    computeFrequency(input, freqs);

    printFrequency(freqs, ALPHABET_SIZE + DIGITS_SIZE);
    
    return 0;
}