输入两个字符串s1，s2，将两个字符串连接起来并复制到字符串s3中，统计s3中的每个数字的个数，大写字母的个数，小写字母的个数和其他字符的个数的C语言

实现如下：

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

int main() {
    char s1[100], s2[100], s3[200];
    int i, digit_count = 0, upper_count = 0, lower_count = 0, other_count = 0;

    printf("Enter string s1: ");
    fgets(s1, sizeof(s1), stdin);
    s1[strcspn(s1, "\n")] = '\0';  // remove newline character

    printf("Enter string s2: ");
    fgets(s2, sizeof(s2), stdin);
    s2[strcspn(s2, "\n")] = '\0';  // remove newline character

    strcpy(s3, s1);
    strcat(s3, s2);

    for (i = 0; s3[i] != '\0'; i++) {
        if (isdigit(s3[i])) {
            digit_count++;
        } else if (isupper(s3[i])) {
            upper_count++;
        } else if (islower(s3[i])) {
            lower_count++;
        } else {
            other_count++;
        }
    }

    printf("s3: %s\n", s3);
    printf("Number of digits: %d\n", digit_count);
    printf("Number of uppercase letters: %d\n", upper_count);
    printf("Number of lowercase letters: %d\n", lower_count);
    printf("Number of other characters: %d\n", other_count);

    return 0;
}

输入示例：

Enter string s1: Hello
Enter string s2: 123world!
s3: Hello123world!
Number of digits: 3
Number of uppercase letters: 1
Number of lowercase letters: 8
Number of other characters: 1