C语言 | Leetcode C语言题解之第468题验证IP地址

题目：

题解：

char * validIPAddress(char * queryIP) {int len = strlen(queryIP);if (strchr(queryIP, '.')) {// IPv4int last = -1;for (int i = 0; i < 4; ++i) {int cur = -1;if (i == 3) {cur = len;} else {char * p = strchr(queryIP + last + 1, '.');if (p) {cur = p - queryIP;}}if (cur < 0) {return "Neither";}if (cur - last - 1 < 1 || cur - last - 1 > 3) {return "Neither";}int addr = 0;for (int j = last + 1; j < cur; ++j) {if (!isdigit(queryIP[j])) {return "Neither";}addr = addr * 10 + (queryIP[j] - '0');}if (addr > 255) {return "Neither";}if (addr > 0 && queryIP[last + 1] == '0') {return "Neither";}if (addr == 0 && cur - last - 1 > 1) {return "Neither";}last = cur;}return "IPv4";}else {// IPv6int last = -1;for (int i = 0; i < 8; ++i) {int cur = -1;if (i == 7) {cur = len;} else {char * p = strchr(queryIP + last + 1, ':');if (p) {cur = p - queryIP;}}if (cur < 0) {return "Neither";}if (cur - last - 1 < 1 || cur - last - 1 > 4) {return "Neither";}for (int j = last + 1; j < cur; ++j) {if (!isdigit(queryIP[j]) && !('a' <= tolower(queryIP[j]) && tolower(queryIP[j]) <= 'f')) {return "Neither";}}last = cur;}return "IPv6";}
}