#include <stdio.h>typedef char bool;
#define true 1
#define false 0/**1.判斷字符串是否形如“192.168.1.1”2.字符串兩端含有空格視為合法ip，形如“    192.168.1.1    ”3.字符串中間含有空格視為非法ip，形如“192.168. 1.2”4.字符串0開頭視為不合法ip，形如192.168.01.15.字符串0.0.0.0視為合法ip*/bool checkIpv4(const char *ip){printf("檢驗對象是：%s\n", ip);if(NULL == ip) {return false;}const char *q = ip;     //字串指針unsigned short int s = 0, count = 0, digitNumber = 0;  //s是字串轉化為的整型，count是 . 的個數, digitNumber 是 . 之間的數量bool hasZero = false;// 開頭有空格while(' ' == *q) {q++;}while('\0' != *q) {if('.' == *q) {// . 前面沒有任何值，則非法if(digitNumber == 0) {return false;}s = 0;digitNumber = 0;count++;hasZero = false;q++;continue;}// 值非法if(*q < '0' || *q > '9') {// 結尾空格if(' ' == *q && 3 == count) {const char *qq = q;while(' ' == *qq) {qq++;}return '\0' == *qq;} else{return false;}}int x = *q - '0';s = s*10 + x;// 0.0.0.0 合法， 00.0.0.0 不合法if(0 == s) {if(hasZero) {return false;} else{hasZero = true;}}if(s > 255) {return false;}digitNumber++;q++;}return (3 == count);
}int main(void){{const int count = 10;char *ip[count] = {"0.0.0.0", "255.255.255.255", "0.10.0.0", " 1.1.1.1", "1.1.1.1 ", " 1.1.1.1 "};for(int i = 0; i < count; i++) {if(checkIpv4(ip[i]))printf("該地址是IPv4地址\n");elseprintf("該地址不是IPv4地址\n");}}printf("\n\n");{const int count = 10;char *ip[count] = {"1.1.1. 1", "1..2.3", "00.1.1.1", "a.1.1.1", };for(int i = 0; i < count; i++) {if(checkIpv4(ip[i]))printf("該地址是IPv4地址\n");elseprintf("該地址不是IPv4地址\n");}}return 0;
}