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[BAEL-8920] Add code for restoring IP address #18109

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[BAEL-8920] Add code for restoring IP address #18109

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39 changes: 39 additions & 0 deletions ...rrays-operations-advanced-3/src/main/java/com/baeldung/restoreipaddress/Backtracking.java
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package com.baeldung.restoreipaddress;

import java.util.ArrayList;
import java.util.List;

public class Backtracking {
public List<String> restoreIPAddresses(String s) {
List<String> result = new ArrayList<>();
backtrack(result, s, new ArrayList<>(), 0);
return result;
}

private void backtrack(List<String> result, String s, List<String> current, int index) {
if (current.size() == 4) {
if (index == s.length()) {
result.add(String.join(".", current));
}
return;
}

for (int len = 1; len <= 3; len++) {
if (index + len > s.length()) break;

String part = s.substring(index, index + len);
if (isValid(part)) {
current.add(part);
backtrack(result, s, current, index + len);
current.remove(current.size() - 1);
}
}
}

private boolean isValid(String part) {
if (part.length() > 1 && part.startsWith("0")) return false;
int num = Integer.parseInt(part);
return num >= 0 && num <= 255;
}
}

42 changes: 42 additions & 0 deletions ...operations-advanced-3/src/main/java/com/baeldung/restoreipaddress/DynamicProgramming.java
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package com.baeldung.restoreipaddress;

import java.util.ArrayList;
import java.util.List;

public class DynamicProgramming {
public List<String> restoreIPAddresses(String s) {
int n = s.length();
if (n < 4 || n > 12) return new ArrayList<>();

List<String>[][] dp = new ArrayList[n + 1][5];
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= 4; j++) {
dp[i][j] = new ArrayList<>();
}
}

dp[0][0].add("");

for (int i = 1; i <= n; i++) {
for (int k = 1; k <= 4; k++) {
for (int j = 1; j <= 3 && i - j >= 0; j++) {
String segment = s.substring(i - j, i);
if (isValid(segment)) {
for (String prefix : dp[i - j][k - 1]) {
dp[i][k].add(prefix.isEmpty() ? segment : prefix + "." + segment);
}
}
}
}
}

return dp[n][4];
}

private boolean isValid(String part) {
if (part.length() > 1 && part.startsWith("0")) return false;
int num = Integer.parseInt(part);
return num >= 0 && num <= 255;
}

}
38 changes: 38 additions & 0 deletions ...a-arrays-operations-advanced-3/src/main/java/com/baeldung/restoreipaddress/Iterative.java
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package com.baeldung.restoreipaddress;

import java.util.ArrayList;
import java.util.List;

public class Iterative {
public List<String> restoreIPAddresses(String s) {
List<String> result = new ArrayList<>();

if (s.length() < 4 || s.length() > 12) {
return result;
}

for (int i = 1; i < 4; i++) {
for (int j = i + 1; j < Math.min(i + 4, s.length()); j++) {
for (int k = j + 1; k < Math.min(j + 4, s.length()); k++) {
String part1 = s.substring(0, i);
String part2 = s.substring(i, j);
String part3 = s.substring(j, k);
String part4 = s.substring(k);

if (isValid(part1) && isValid(part2) && isValid(part3) && isValid(part4)) {
result.add(part1 + "." + part2 + "." + part3 + "." + part4);
}
}
}
}
return result;
}

private boolean isValid(String part) {
if (part.length() > 1 && part.charAt(0) == '0') {
return false;
}
int num = Integer.parseInt(part);
return num >= 0 && num <= 255;
}
}
66 changes: 66 additions & 0 deletions ...erations-advanced-3/src/test/java/com/baeldung/restoreipaddress/BacktrackingUnitTest.java
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package com.baeldung.restoreipaddress;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.util.List;

import org.junit.jupiter.api.Test;

public class BacktrackingUnitTest {
Backtracking backtracking = new Backtracking();

@Test
public void givenValidInput_whenUsingBacktracking_thenRestoreIPAddress() {
String input = "25525511135";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.contains("255.255.11.135"));
assertTrue(result.contains("255.255.111.35"));
assertEquals(2, result.size());
}

@Test
public void givenMinimumLength_whenUsingBacktracking_thenRestoreIPAddress() {
String input = "4567";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.contains("4.5.6.7"));
assertEquals(1, result.size());
}

@Test
public void givenEmptyString_whenUsingBacktracking_thenReturnEmptyList() {
String input = "";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLongString_whenUsingBacktracking_thenReturnEmptyList() {
String input = "123456789012345";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenShortString_whenUsingBacktracking_thenReturnEmptyList() {
String input = "456";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenInvalidParts_whenUsingBacktracking_thenReturnEmptyList() {
String input = "265265278294";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLeadingZeros_whenUsingBacktracking_thenRestoreIPAddress() {
String input = "010010";
List<String> result = backtracking.restoreIPAddresses(input);
assertTrue(result.contains("0.10.0.10"));
assertTrue(result.contains("0.100.1.0"));
assertEquals(2, result.size());
}
}
66 changes: 66 additions & 0 deletions ...ns-advanced-3/src/test/java/com/baeldung/restoreipaddress/DynamicProgrammingUnitTest.java
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package com.baeldung.restoreipaddress;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.util.List;

import org.junit.jupiter.api.Test;

public class DynamicProgrammingUnitTest {
DynamicProgramming dynamicProgramming = new DynamicProgramming();

@Test
public void givenValidInput_whenUsingIterative_thenRestoreIPAddress() {
String input = "25525511135";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.contains("255.255.11.135"));
assertTrue(result.contains("255.255.111.35"));
assertEquals(2, result.size());
}

@Test
public void givenMinimumLength_whenUsingIterative_thenRestoreIPAddress() {
String input = "4567";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.contains("4.5.6.7"));
assertEquals(1, result.size());
}

@Test
public void givenEmptyString_whenUsingIterative_thenReturnEmptyList() {
String input = "";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLongString_whenUsingIterative_thenReturnEmptyList() {
String input = "123456789012345";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenShortString_whenUsingIterative_thenReturnEmptyList() {
String input = "456";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenInvalidParts_whenUsingIterative_thenReturnEmptyList() {
String input = "265265278294";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLeadingZeros_whenUsingIterative_thenRestoreIPAddress() {
String input = "010010";
List<String> result = dynamicProgramming.restoreIPAddresses(input);
assertTrue(result.contains("0.10.0.10"));
assertTrue(result.contains("0.100.1.0"));
assertEquals(2, result.size());
}
}
63 changes: 63 additions & 0 deletions ...-operations-advanced-3/src/test/java/com/baeldung/restoreipaddress/IterativeUnitTest.java
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package com.baeldung.restoreipaddress;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
import java.util.List;

public class IterativeUnitTest {
Iterative iterative = new Iterative();

@Test
public void givenValidInput_whenUsingIterative_thenRestoreIPAddress() {
String input = "25525511135";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.contains("255.255.11.135"));
assertTrue(result.contains("255.255.111.35"));
assertEquals(2, result.size());
}

@Test
public void givenMinimumLength_whenUsingIterative_thenRestoreIPAddress() {
String input = "4567";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.contains("4.5.6.7"));
assertEquals(1, result.size());
}

@Test
public void givenEmptyString_whenUsingIterative_thenReturnEmptyList() {
String input = "";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLongString_whenUsingIterative_thenReturnEmptyList() {
String input = "123456789012345";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenShortString_whenUsingIterative_thenReturnEmptyList() {
String input = "456";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenInvalidParts_whenUsingIterative_thenReturnEmptyList() {
String input = "265265278294";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.isEmpty());
}

@Test
public void givenLeadingZeros_whenUsingIterative_thenRestoreIPAddress() {
String input = "010010";
List<String> result = iterative.restoreIPAddresses(input);
assertTrue(result.contains("0.10.0.10"));
assertTrue(result.contains("0.100.1.0"));
assertEquals(2, result.size());
}
}