题解 | #验证IP地址#

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 验证IP地址
 * @param IP string字符串 一个IP地址字符串
 * @return string字符串
 */
#include <string.h>
int  ipv4(char* IP) {
    char* p = IP;
    int num = 0;
    int d = 0;
    do {
        if (*p == '.' || *p == '\0') {
            if (num > 255) return -1;
            d++;
            num = 0;
            if (*p == '\0') break ;
            p++;
        }
        if (*p >= '0' && *p < '9') {
            if (num == 0 && *p == '0' && *(p + 1) != '.') {
                return -1;
            }
            num = (*p - '0') + num * 10;
        } else {
            return -1;
        }
    } while (*p++ != '\0');
    if (d != 4) return -1;
    return 0;
}

int  ipv6(char* IP) {
    char* p = IP;
    int num = 0;
    int d = 1;
    do {
        if (*p == ':' || *p == '\0') {
            if(num==0||num>4){
                return -1;
            }
            d++;
            num=0;
            if(*p=='\0'){
                break;
            }
            p++;
        }
        if ((*p >= '0' && *p <= '9' )||( *p >= 'a' && *p <= 'f' )|| (*p >= 'A' &&
                *p <= 'F')) {
            p++;
            num++;
        } else {
            return -1;
        }
    } while (*p != '\0');
    if (d != 8) {
        return -1;
    }
    return 0;

}

char* solve(char* IP ) {
    // write code here
    char* p = IP;
    int flag = 0;
    while (*p != '\0') {
        if (*p == '.') {
            flag = 1;
            break;
        }
        if (*p == ':') {
            flag = -1;
            break ;
        }
        p++;
    }
    if (flag == 1) {
        if (ipv4(IP) == 0) {
            return "IPv4";
        }
    }
    if (flag == -1) {
        if (ipv6(IP) == 0) {
            return "IPv6";
        }
    }

    return "Neither";

}