Program to validate an IP address
Last Updated :
15 Jul, 2025
Find whether a given IP address is valid. An IP address is a unique identifier for devices on a network, enabling internet communication. It has two versions: IPv4 and IPv6. We will validate IPv4 and IPv6 addresses separately.
IPv4 Addresses Validation
IPv4 addresses use dot-decimal notation, consisting of four numbers (0-255) separated by dots, e.g., 172.16.254.1.
Example
Input: s = "128.0.0.1";
Output: true
Explantaion: Each section split by '.' contains only digits, has no leading zeros, and lies within the range 0-255.
Input: s = "125.16.100.1";
Output: true
Explanation: Each section split by '.' contains only digits, has no leading zeros, and lies within the range 0-255.
Input: s = "125.512.100.1";
Output: false
Explanation: Each section must be within the range 0-255, but 512 exceeds this limit, making the IP invalid.
Input: s = "125.512.100.abc"
Output: false
Explanation: Each section must contain only numeric values, but "abc" is not a valid integer, making the IP invalid.
[Naive Approach] Using the Inbulit Library Methods - O(n) Time and O(n) Space
We use built-in library methods like split() in Python and Java, and stringstream in C++ to split the string by .. Then, we check if each segment lies within the range 0-255. If all segments satisfy this condition, it is a valid IPv4 address; otherwise, it is not.
C++
#include <bits/stdc++.h>
using namespace std;
int isValid(string &s){
int n = s.size();
if (n < 7)
return false;
// Using string stream to separate all
// the string from '.' and push back
// into vector like for ex -
vector<string> v;
stringstream ss(s);
while (ss.good()){
string substr;
getline(ss, substr, '.');
v.push_back(substr);
}
if (v.size() != 4)
return false;
// Iterating over the generated vector of strings
for (int i = 0; i < v.size(); i++){
string temp = v[i];
if (temp.size() > 1){
if (temp[0] == '0')
return false;
}
for (int j = 0; j < temp.size(); j++){
if (isalpha(temp[j]))
return false;
}
// And lastly we are checking if the
// number is greater than 255 or not
if (stoi(temp) > 255)
return false;
}
return true;
}
int main(){
string s = "128.0.0.1";
isValid(s) ? cout << "true" : cout << "false";
return 0;
}
import java.util.StringTokenizer;
class GfG {
static boolean isValid(String s){
int n = s.length();
if (n < 7)
return false;
// Using StringTokenizer to
// separate all the strings
// from '.' and push back into
// vector like for example -
StringTokenizer st = new StringTokenizer(s, ".");
int count = 0;
while (st.hasMoreTokens()) {
String substr = st.nextToken();
count++;
// If the substring size
// is greater than 1 and
// the first character is
// '0', return false
if (substr.length() > 1
&& substr.charAt(0) == '0')
return false;
for (int j = 0; j < substr.length(); j++) {
if (!Character.isDigit(substr.charAt(j)))
return false;
}
// Check if the number is greater than 255
if (Integer.parseInt(substr) > 255)
return false;
}
if (count != 4)
return false;
return true;
}
public static void main(String[] args){
String s = "128.0.0.1";
System.out.println(isValid(s) ? "true": "false");
}
}
def isValid(s):
n = len(s)
if n < 7:
return False
# Using split to separate all the
# strings from '.' and create
# a list like for example-
substrings = s.split(".")
count = 0
for substr in substrings:
count += 1
# If the substring size is
# greater than 1 and the first
# character is '0', return false
if len(substr) > 1 and substr[0] == '0':
return False
# For substrings like a.b.c.d, checking if
# any character is non-numeric
if not substr.isdigit():
return False
# Check if the number is greater than 255
if int(substr) > 255:
return False
# If the count of substrings
# is not 4, return false
if count != 4:
return False
return True
if __name__ == "__main__":
s = "128.0.0.1"
print("true" if isValid(s) else "false")
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
class GfG {
static bool IsValidIP(string s){
int n = s.Length;
if (n < 7)
return false;
// Using regex to match and separate
// all the strings from '.'
var matches = Regex.Matches(
s, @"\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b");
// If the number of matches
// is not 1, return false
if (matches.Count != 1)
return false;
var ipString = matches[0].Value;
// Split the IP string by '.'
// and store in an array
string[] parts = ipString.Split('.');
// If the array length != 4,
// return false
if (parts.Length != 4)
return false;
// Iterating over the
// array of strings
for (int i = 0; i < parts.Length; i++) {
string temp = parts[i];
if (temp.Length > 1 && temp[0] == '0')
return false;
if (temp.Any(char.IsLetter))
return false;
// Check if the number is
// greater than 255
if (int.Parse(temp) > 255)
return false;
}
return true;
}
static void Main(){
string s = "128.0.0.1";
Console.WriteLine(IsValidIP(s) ? "true": "false");
}
}
function isValidIP(s){
const n = s.length;
if (n < 7)
return false;
const v = s.split(".");
if (v.length !== 4)
return false;
for (let i = 0; i < v.length; i++) {
const temp = v[i];
if (temp.length > 1 && temp[0] === "0")
return false;
for (let j = 0; j < temp.length; j++) {
if (isNaN(temp[j]))
return false;
}
if (parseInt(temp) > 255)
return false;
}
return true;
}
//Driver Code
const s = "128.0.0.1";
isValidIP(s) ? console.log("true"): console.log("false");
[Expected Approach] Using Traversal over the IP String - O(n) Time and O(1) Space
Iterate through the given string, extracting each section separated by .. Check if each section consists only of numeric characters and falls within the range 0-255. If any section fails these conditions, return "false", otherwise, return "true."
C++
#include <bits/stdc++.h>
using namespace std;
bool valid_part(string &s){
int n = s.length();
// Length must be between 1 and 3
if (n == 0 || n > 3)
return false;
// Check if all characters are digits
for (char c : s)
{
if (c < '0' || c > '9')
return false;
}
// Prevent numbers like "00", "01"
if (s[0] == '0' && n > 1)
return false;
// Convert to integer manually
int num = 0;
for (char c : s)
{
num = num * 10 + (c - '0');
}
return num >= 0 && num <= 255;
}
// Function to check if a given
// string is a valid IPv4 address
bool isValid( string &ip){
istringstream ss(ip);
string part;
int segmentCount = 0;
while (getline(ss, part, '.'))
{
if (!valid_part(part))
return false;
segmentCount++;
}
return segmentCount == 4;
}
int main()
{
string s = "128.0.0.1";
cout << (isValid(s) ? "true" : "false");
return 0;
}
import java.util.StringTokenizer;
public class GfG {
static boolean isValidPart(String s){
int n = s.length();
if (n > 3)
return false;
for (int i = 0; i < n; i++)
if (!(s.charAt(i) >= '0' && s.charAt(i) <= '9'))
return false;
if (s.indexOf('0') == 0 && n > 1)
return false;
try {
int x = Integer.parseInt(s);
// The string is valid if the number
// generated is between 0 to 255
return (x >= 0 && x <= 255);
}
catch (NumberFormatException e) {
return false;
}
}
static int isValid(String ipStr){
// If the empty string then return false
if (ipStr == null)
return 0;
int dots = 0;
int len = ipStr.length();
int count = 0;
for (int i = 0; i < len; i++)
if (ipStr.charAt(i) == '.')
count++;
if (count != 3)
return 0;
// Using StringTokenizer to
// split the IP string
StringTokenizer st
= new StringTokenizer(ipStr, ".");
while (st.hasMoreTokens()) {
String part = st.nextToken();
// After parsing string,
// it must be valid
if (isValidPart(part)) {
// Parse remaining string
if (st.hasMoreTokens())
dots++;
}
else
return 0;
}
if (dots != 3)
return 0;
return 1;
}
public static void main(String[] args){
String s = "128.0.0.1";
System.out.println(isValid(s) == 1 ? "true": "false");
}
}
def valid_part(s):
n = len(s)
if n == 0 or n > 3:
return False
if not s.isdigit():
return False
if s[0] == '0' and n > 1:
return False
num = int(s)
# The string is valid if the number
# generated is between 0 to 255
return 0 <= num <= 255
def isValid(ip):
# If the empty string then return false
parts = ip.split('.')
if len(parts) != 4:
return False
for part in parts:
if not valid_part(part):
return False
return True
if __name__ == "__main__":
s = "128.0.0.1"
print("true" if isValid(s) else "false")
using System;
using System.Text.RegularExpressions;
class GfG {
static bool ValidPart(string s){
int n = s.Length;
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'))
return false;
}
string str = s;
if (str.IndexOf('0') == 0 && n > 1)
return false;
// the string is valid if the number
// generated is between 0 to 255
if (int.TryParse(str, out int x)) {
return (x >= 0 && x <= 255);
}
return false;
}
static int IsValidIP(string ipStr){
if (ipStr == null)
return 0;
int count = 0;
int len = ipStr.Length;
for (int i = 0; i < len; i++) {
if (ipStr[i] == '.') {
count++;
}
}
if (count != 3) {
return 0;
}
string[] parts = ipStr.Split('.');
if (parts.Length != 4) {
return 0;
}
foreach(string part in parts){
if (!ValidPart(part)) {
return 0;
}
}
return 1;
}
static void Main(string[] args){
string s = "128.0.0.1";
Console.WriteLine(IsValidIP(s) == 1 ? "true" : "false");
}
}
function validPart(s){
const n = s.length;
if (n > 3) {
return false;
}
// Check if the string only
// contains digits, if not,
// return false
for (let i = 0; i < n; i++) {
if (!(s[i] >= "0" && s[i] <= "9")) {
return false;
}
}
// Convert the string to an integer
const x = parseInt(s);
// The string is valid if
// the number generated is
// between 0 to 255
return (x >= 0 && x <= 255);
}
// Return true if the IP string
// is valid, else return false
function isValid(ipStr){
// If the string is empty,
// return false
if (ipStr === null) {
return false;
}
const parts = ipStr.split(".");
let count = 0;
for (let i = 0; i < ipStr.length; i++) {
if (ipStr[i] === ".") {
count++;
}
}
if (count !== 3) {
return false;
}
for (let i = 0; i < parts.length; i++) {
if (!validPart(parts[i])) {
return false;
}
}
return true;
}
// Driver Code
const s = "128.0.0.1";
isValid(s) ? console.log("true"): console.log("false");
IPv6 Addresses Validation
IPv6 addresses use hexadecimal colon notation, with eight groups of four hex digits (0-9, A-F) separated by colons, e.g., 2001:db8:85a3::8a2e:370:7334.
Examples
Input: s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
Output: true
Explanation: Each section split by : contains only hexadecimal digits (0-9, a-f, A-F) and is within the valid length of 1 to 4 characters.
Input: s = "FE80::1";
Output: false
Explanation: The IPv6 address not have 8 section.
Input: s = "2001:85a3::8a2e:0370:733400";
Output: false
Explanation: Each section must be between 1 to 4 hexadecimal characters, but "733400" exceeds this limit, making the IP invalid.
Input: s = "2001:GHI8:85a3:0000:0000:8a2e:0370:7334";
Output: false
Explanation: Each section must contain only valid hexadecimal characters (0-9, a-f, A-F), but "GHI8" includes invalid characters, making the IP invalid.
[Naive Approach] Using the Inbulit Library Methods - O(n) Time and O(n) Space
The approach splits the IPv6 address into segments using built-in functions (e.g., split in Python/Java, stringstream in C++). Each segment is checked to ensure it contains only valid hexadecimal characters (0-9, a-f, A-F) and is between 1 to 4 characters long. If the total segments are not exactly 8, or any segment is invalid, the IPv6 address is considered invalid.
C++
#include <bits/stdc++.h>
using namespace std;
bool isValid(string &s){
int n = s.size();
if (n < 15)
return false;
vector<string> v;
stringstream ss(s);
while (ss.good()){
string substr;
getline(ss, substr, ':');
v.push_back(substr);
}
if (v.size() != 8)
return false;
for (int i = 0; i < v.size(); i++){
string temp = v[i];
if (temp.empty() || temp.size() > 4)
return false;
for (char c : temp){
if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')))
return false;
}
}
return true;
}
int main(){
string s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
isValid(s) ? cout << "true" : cout << "false";
return 0;
}
import java.util.*;
class GfG {
static boolean isValid(String s){
if (s.length() < 15)
return false;
String[] parts = s.split(":");
if (parts.length != 8)
return false;
for (String part : parts) {
if (part.isEmpty() || part.length() > 4)
return false;
for (char c : part.toCharArray()) {
if (!((c >= '0' && c <= '9')
|| (c >= 'a' && c <= 'f')
|| (c >= 'A' && c <= 'F')))
return false;
}
}
return true;
}
public static void main(String[] args){
String s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
System.out.println(isValid(s) ? "true": "false");
}
}
def isValid(s):
if len(s) < 15:
return False
parts = s.split(":")
if len(parts) != 8:
return False
for part in parts:
if len(part) == 0 or len(part) > 4:
return False
for c in part:
if not (c.isdigit() or 'a' <= c <= 'f' or 'A' <= c <= 'F'):
return False
return True
if __name__ == "__main__":
s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334"
print("true" if isValid(s) else "false")
using System;
class GfG {
static bool isValid(string s){
if (s.Length < 15)
return false;
string[] parts = s.Split(':');
if (parts.Length != 8)
return false;
foreach(string part in parts){
if (part.Length == 0 || part.Length > 4)
return false;
foreach(char c in part){
if (!((c >= '0' && c <= '9')
|| (c >= 'a' && c <= 'f')
|| (c >= 'A' && c <= 'F')))
return false;
}
}
return true;
}
static void Main(){
string s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
Console.WriteLine(isValid(s) ? "true": "false");
}
}
function isValid(s){
if (s.length < 15)
return false;
let parts = s.split(":");
if (parts.length !== 8)
return false;
for (let part of parts) {
if (part.length === 0 || part.length > 4)
return false;
for (let c of part) {
if (!((c >= "0" && c <= "9")
|| (c >= "a" && c <= "f")
|| (c >= "A" && c <= "F")))
return false;
}
}
return true;
}
let s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
console.log(isValid(s) ? "true" : "false");
[Expected Approach] Using Traversal over the IP string - O(n) Time and O(1) Space
Iterate through the given string, split the string by ':', ensuring it has 8 sections. Verify each section contains only hexadecimal characters (0-9, a-f, A-F) and is 1-4 characters long. Return "true" if all conditions are met; otherwise, return 'false'.
C++
#include <bits/stdc++.h>
using namespace std;
bool isValidSegment(string &s){
int n = s.length();
// Length must be between 1 and 4
if (n == 0 || n > 4)
return false;
// Check if all characters are
// valid hexadecimal digits
for (char c : s){
if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')))
return false;
}
return true;
}
bool isValid( string &ip){
int colonCount = 0;
int len = ip.length();
// Count the number of colons
for (char c : ip){
if (c == ':')
colonCount++;
}
// An IPv6 address must
// have exactly 7 colons
if (colonCount != 7)
return false;
// Split manually by ':'
string segment;
int segmentCount = 0;
for (int i = 0; i < len; i++){
if (ip[i] == ':'){
if (!isValidSegment(segment))
return false;
segment.clear();
segmentCount++;
}
else{
segment += ip[i];
}
}
if (!isValidSegment(segment))
return false;
return segmentCount == 7;
}
int main(){
string s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
cout << (isValid(s) ? "true" : "false");
return 0;
}
import java.util.*;
public class GfG {
public static boolean isValidSegment(String s) {
int n = s.length();
if (n == 0 || n > 4) return false;
for (char c : s.toCharArray()) {
// Only hexadecimal characters allowed
if (!Character.isDigit(c) && !(c >= 'a' && c <= 'f') && !(c >= 'A' && c <= 'F')) {
return false;
}
}
return true;
}
public static boolean isValid(String ip) {
if (ip == null || ip.isEmpty()) return false;
String[] segments = ip.split(":");
// IPv6 must have exactly 8 segments
if (segments.length != 8) return false;
for (String segment : segments) {
if (!isValidSegment(segment)) return false;
}
return true;
}
public static void main(String[] args) {
String s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
System.out.println((isValid(s) ? "true" : "false"));
}
}
def is_valid_segment(segment):
if not (1 <= len(segment) <= 4):
return False
for char in segment:
# Only hexadecimal characters allowed
if not (char.isdigit() or 'a' <= char.lower() <= 'f'):
return False
return True
def isValid(ip):
if not ip:
return False
segments = ip.split(":")
# IPv6 must have exactly 8 segments
if len(segments) != 8:
return False
return all(is_valid_segment(segment) for segment in segments)
if __name__ == "__main__":
s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334"
print(f"{'true' if isValid(s) else 'false'}")
using System;
class GfG {
static bool IsValidSegment(string s){
int n = s.Length;
if (n == 0 || n > 4)
return false;
foreach(char c in s){
if (!((c >= '0' && c <= '9')
|| (c >= 'a' && c <= 'f')
|| (c >= 'A' && c <= 'F')))
return false;
}
return true;
}
static bool IsValid(string ip){
int colonCount = 0;
int len = ip.Length;
foreach(char c in ip){
if (c == ':')
colonCount++;
}
if (colonCount != 7)
return false;
string segment = "";
int segmentCount = 0;
for (int i = 0; i < len; i++) {
if (ip[i] == ':') {
if (!IsValidSegment(segment))
return false;
segment = "";
segmentCount++;
}
else {
segment += ip[i];
}
}
if (!IsValidSegment(segment))
return false;
return segmentCount == 7;
}
static void Main(){
string s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
Console.WriteLine(IsValid(s) ? "true": "false");
}
}
function isValidSegment(s){
const n = s.length;
if (n === 0 || n > 4) {
return false;
}
for (let i = 0; i < n; i++) {
const c = s[i];
if (!((c >= "0" && c <= "9")
|| (c >= "a" && c <= "f")
|| (c >= "A" && c <= "F"))) {
return false;
}
}
return true;
}
function isValid(ip){
let colonCount = 0;
const len = ip.length;
for (let i = 0; i < len; i++) {
if (ip[i] === ":") {
colonCount++;
}
}
if (colonCount !== 7) {
return false;
}
let segment = "";
let segmentCount = 0;
for (let i = 0; i < len; i++) {
if (ip[i] === ":") {
if (!isValidSegment(segment)) {
return false;
}
segment = "";
segmentCount++;
}
else {
segment += ip[i];
}
}
if (!isValidSegment(segment)) {
return false;
}
return segmentCount === 7;
}
const s = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
console.log(isValid(s) ? "true" : "false");
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Introduction to RecursionThe process in which a function calls itself directly or indirectly is called recursion and the corresponding function is called a recursive function. A recursive algorithm takes one step toward solution and then recursively call itself to further move. The algorithm stops once we reach the solution
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Greedy AlgorithmsGreedy algorithms are a class of algorithms that make locally optimal choices at each step with the hope of finding a global optimum solution. At every step of the algorithm, we make a choice that looks the best at the moment. To make the choice, we sometimes sort the array so that we can always get
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Graph AlgorithmsGraph is a non-linear data structure like tree data structure. The limitation of tree is, it can only represent hierarchical data. For situations where nodes or vertices are randomly connected with each other other, we use Graph. Example situations where we use graph data structure are, a social net
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Dynamic Programming or DPDynamic Programming is an algorithmic technique with the following properties.It is mainly an optimization over plain recursion. Wherever we see a recursive solution that has repeated calls for the same inputs, we can optimize it using Dynamic Programming. The idea is to simply store the results of
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Bitwise AlgorithmsBitwise algorithms in Data Structures and Algorithms (DSA) involve manipulating individual bits of binary representations of numbers to perform operations efficiently. These algorithms utilize bitwise operators like AND, OR, XOR, NOT, Left Shift, and Right Shift.BasicsIntroduction to Bitwise Algorit
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Advanced
Segment TreeSegment Tree is a data structure that allows efficient querying and updating of intervals or segments of an array. It is particularly useful for problems involving range queries, such as finding the sum, minimum, maximum, or any other operation over a specific range of elements in an array. The tree
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Pattern SearchingPattern searching algorithms are essential tools in computer science and data processing. These algorithms are designed to efficiently find a particular pattern within a larger set of data. Patten SearchingImportant Pattern Searching Algorithms:Naive String Matching : A Simple Algorithm that works i
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GeometryGeometry is a branch of mathematics that studies the properties, measurements, and relationships of points, lines, angles, surfaces, and solids. From basic lines and angles to complex structures, it helps us understand the world around us.Geometry for Students and BeginnersThis section covers key br
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