用c语言编写程序编写程序实现两个超长整数大于等于0每个最长80位数字的乘法运算。

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

#define MAX_LEN 81

void reverse(char *str) {
    int len = strlen(str);
    for (int i = 0; i < len / 2; i++) {
        char tmp = str[i];
        str[i] = str[len - i - 1];
        str[len - i - 1] = tmp;
    }
}

void multiply(char *a, char *b, char *result) {
    int len_a = strlen(a);
    int len_b = strlen(b);
    int len_result = len_a + len_b;
    int carry = 0;
    memset(result, '0', len_result);

    reverse(a);
    reverse(b);

    for (int i = 0; i < len_a; i++) {
        carry = 0;
        for (int j = 0; j < len_b; j++) {
            int digit = (a[i] - '0') * (b[j] - '0') + (result[i+j] - '0') + carry;
            carry = digit / 10;
            result[i+j] = digit % 10 + '0';
        }
        if (carry > 0) {
            result[i+len_b] += carry;
        }
    }

    reverse(result);
    while (result[0] == '0' && len_result > 1) {
        memmove(result, result + 1, len_result - 1);
        len_result--;
    }
    result[len_result] = '\0';
}

int main() {
    char a[MAX_LEN];
    char b[MAX_LEN];
    char result[MAX_LEN * 2];

    printf("Enter the first number: ");
    scanf("%s", a);
    printf("Enter the second number: ");
    scanf("%s", b);

    multiply(a, b, result);
    printf("The result is: %s\n", result);

    return 0;
}
``