编写一个程序来验证 IPv4 地址。
根据维基百科，IPv4 地址以点十进制表示法表示，它由四个十进制数字组成，每个数字的范围从 0 到 255，用点分隔，例如 172.16.254.1
以下是检查给定字符串是否为有效 IPv4 地址的步骤：
步骤 1)用“.”解析字符串 使用“ strtok() ”函数作为分隔符。
输出
egptr = strtok(str, DELIM);步骤 2) A) 如果 ptr 包含任何不是数字的字符，则返回 0 B) 将“ptr”转换为十进制数字，例如 'NUM' C) 如果 NUM 不在 0-255 范围内，则返回 0 D) 如果 NUM 在范围为 0-255 且 ptr 为非 NULL 将“dot_counter”递增 1 E) 如果 ptr 为 NULL 则转到步骤 3 否则转到步骤 1 步骤 3)如果 dot_counter != 3 返回 0 否则返回 1
// Program to check if a given
// string is valid IPv4 address or not
#include <bits/stdc++.h>
using namespace std;
#define DELIM "."
/* function to check whether the
string passed is valid or not */
bool valid_part(char* s)
{
int n = strlen(s);
// if length of passed string is
// more than 3 then it is not valid
if (n > 3)
return false;
// check if the string only contains digits
// if not then return false
for (int i = 0; i < n; i++)
if ((s[i] >= '0' && s[i] <= '9') == false)
return false;
string str(s);
// if the string is "00" or "001" or
// "05" etc then it is not valid
if (str.find('0') == 0 && n > 1)
return false;
stringstream geek(str);
int x;
geek >> x;
// the string is valid if the number
// generated is between 0 to 255
return (x >= 0 && x <= 255);
}
/* return 1 if IP string is
valid, else return 0 */
int is_valid_ip(char* ip_str)
{
// if empty string then return false
if (ip_str == NULL)
return 0;
int i, num, dots = 0;
int len = strlen(ip_str);
int count = 0;
// the number dots in the original
// string should be 3
// for it to be valid
for (int i = 0; i < len; i++)
if (ip_str[i] == '.')
count++;
if (count != 3)
return false;
// See following link for strtok()
char *ptr = strtok(ip_str, DELIM);
if (ptr == NULL)
return 0;
while (ptr) {
/* after parsing string, it must be valid */
if (valid_part(ptr))
{
/* parse remaining string */
ptr = strtok(NULL, ".");
if (ptr != NULL)
++dots;
}
else
return 0;
}
/* valid IP string must contain 3 dots */
// this is for the cases such as 1...1 where
// originally the no. of dots is three but
// after iteration of the string we find
// it is not valid
if (dots != 3)
return 0;
return 1;
}
// Driver code
int main()
{
char ip1[] = "128.0.0.1";
char ip2[] = "125.16.100.1";
char ip3[] = "125.512.100.1";
char ip4[] = "125.512.100.abc";
is_valid_ip(ip1) ? cout<<"Validn" : cout<<"Not validn";
is_valid_ip(ip2) ? cout<<"Validn" : cout<<"Not validn";
is_valid_ip(ip3) ? cout<<"Validn" : cout<<"Not validn";
is_valid_ip(ip4) ? cout<<"Validn" : cout<<"Not validn";
return 0;
}Valid Valid Not valid Not valid
