Determine the validity of an IP address

/************************************************************************* 
 

	> File Name:newfile1.cpp > Author:pzz > Mail:837157806@qq.com > Created time:2014/2/24 14:06:47 * * * /#include <iostream> #include < cstring> #include <cstdio> #include <cstdlib> #include <list> #include <string> #include <

algorithm> #include <iterator> #include <ctype.h> using namespace std;
   inline bool isOK (string Str,int num) {int len=str.length ();

   int d=0;
   if (num!=0&&str[0]== ') return false;
   if (str== "0") return true; if (len>1&&str[0]== ' 0 ') return false;

   Has a leading 0, illegal//cout<< "str=" <<str<< ", num=" <<num<<endl;
	   for (int i=0;i<len;i++) {//if (str[0]== ') cout<< ' Kongge ' <<endl;

	   if (!isdigit (str[i]) &&str[i]!= ') return false; if (str[i]== ') {if (num==2| |
		   NUM==3) return false; else {//if (num==1&&str[0]== ') return false;
			   if (num==4&&str if (num==1&&i!=0&&str[i]== ') return false;
		   if (num==4&&i!=len-1&&str[i]== ') return false;
	   }//if (&&str[i]== ') if (IsDigit (str[i)) {d=d*10+str[i]-' 0 ';
   }//cout<< "d=" <<d<<endl; } if (d<0| |
   d>255) return false;
return true;
    BOOL Isipaddressvalid (const char* PSZIPADDR) {//Please implement if (Pszipaddr==null) return false here;
    String str=string (PSZIPADDR);
	cout<<str<<endl;

	int Len=str.length ();   int coma_num;  =numberofcoma (str);

	Count number, if the number of dots is not equal to 3 is illegal//at the end of STR plus a decimal point, in order to statistically convenient str.append ("."); The following starts the split string, split with the point number, get each string, if the string, illegal, then return false, illegal cases include a space in the middle of the string, the string has a leading 0, the number in the string is no longer between 0-255, and the string is empty, these are illegal//
    
    String::iterator Iter_pre=str.begin (), iter_post;
	int iter_pre=0;
int Iter_post=str.find ('. ', iter_pre);
	cout<<iter_post<<endl;
	if (Iter_post==str.npos) return false; Coma_num=0;
		while (Iter_post!=str.npos) {coma_num++;
		String Substr=str.substr (Iter_pre,iter_post-iter_pre);
		if (substr== "") return false;
        cout<<coma_num<< "," <<substr<<endl;
		if (!isok (substr,coma_num))//If not valid, jumps out and returns false {return false;
		
		} iter_pre=iter_post+1;   
	if (iter_pre<=len-1) iter_post=str.find ('. ', iter_pre);
    } if (coma_num!=4) return false;
return true;
 int main (void) {const char *psz= "123";
 if (Isipaddressvalid (psz)) cout<< "OK" <<endl;
 
 else cout<< "No" <<endl;
 System ("pause");
return 0; }

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The Find and SUBSTR functions of C + + are used:

int find (char c, int pos = 0) const;//Look for the character C at the position of the current string int found (const char *s, int pos = 0) const;//Look up the string s in the current string from POS Position int Find (const char *s, int pos, int n) const;//look up the position of the first n characters in the string s in the current string by starting with the POS int found (const string &s, int pos = 0) C onst;//from Pos to find the position of string s in the current string//Find the location of success, return the value of String::npos int rfind (char c, int pos = NPOs) const;//
Look up the character C in the current string from the point of POS int rfind (const char *s, int pos = NPOs) const;
int rfind (const char *s, int pos, int n = npos) const;
int RFind (const string &s,int pos = NPOs) const; From the beginning of the POS to find the position of the first n characters in the string s in the current string, successfully return to the location, and return string::npos value int find_first_of (char c, int pos = 0) const;//
Starting from Pos Find the first occurrence of the character c the position int find_first_of (const char *s, int pos = 0) const;
int find_first_of (const char *s, int pos, int n) const;
int find_first_of (const string &s,int pos = 0) const; Starts from the POS to find the position of the first character in the current string in an array of the top n characters of S.
Lookup failure Returns string::npos int find_first_not_of (char c, int pos = 0) const;
int find_first_not_of (const char *s, int pos = 0) const; Intfind_first_not_of (const char *s, int pos,int n) const;
int find_first_not_of (const string &s,int pos = 0) const;
Finds the first occurrence of a character not in string s from the current string, and the failure returns STRING::NPOS int find_last_of (char c, int pos = NPOs) const;
int find_last_of (const char *s, int pos = NPOs) const;
int find_last_of (const char *s, int pos, int n = npos) const; 
int find_last_of (const string &s,int pos = NPOs) const;
int find_last_not_of (char c, int pos = NPOs) const;
int find_last_not_of (const char *s, int pos = NPOs) const;
int find_last_not_of (const char *s, int pos, int n) const;
int find_last_not_of (const string &s,int pos = NPOs) const; Find_last_of and find_last_not_of are similar to find_first_of and find_first_not_of, just looking forward from the back

These are the functions in the string class, in addition, in the C + + STL also provides the Find function on the use of each container