Add problem 131

Author: juchanei

src/main/java/io/github/juchanei/leetcodeJava/PalindromePartitioning.java

@@ -0,0 +1,101 @@
+package io.github.juchanei.leetcodeJava;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class PalindromePartitioning {
+    public List<List<String>> partition(String s) {
+        if (s.length() == 0) {
+            return List.of(List.of());
+        }
+
+        List<List<String>> ret = new ArrayList<>();
+        for (int i = 0; i <= s.length(); i++) {
+            String candidate = s.substring(0, i);
+
+            if (!isPalindrome(candidate)) continue;
+
+            partition(s.substring(i))
+                .stream()
+                .map(strings -> Stream
+                    .concat(Stream.of(candidate), strings.stream())
+                    .collect(Collectors.toList()))
+                .forEach(strings -> ret.add(strings));
+        }
+
+        return ret;
+    }
+
+    public boolean isPalindrome(String candidate) {
+        int length = candidate.length();
+        if (length == 0) return false;
+        if (length == 1) return true;
+
+        for (int i = 0; i < (length / 2); i++)
+            if (candidate.charAt(i) != candidate.charAt(length - 1 - i))
+                return false;
+
+        return true;
+    }
+
+
+    public static class UnitTest {
+        private PalindromePartitioning pp = new PalindromePartitioning();
+
+        @Test
+        public void example1() {
+            String input = "aab";
+            List<List<String>> output = Arrays.asList(
+                Arrays.asList("a","a","b"),
+                Arrays.asList("aa","b")
+            );
+
+            Assert.assertArrayEquals(
+                output.toArray(),
+                pp.partition(input).toArray()
+            );
+        }
+
+        @Test
+        public void example2() {
+            String input = "a";
+            List<List<String>> output = Arrays.asList(
+                Arrays.asList("a")
+            );
+
+            Assert.assertArrayEquals(
+                output.toArray(),
+                pp.partition(input).toArray()
+            );
+        }
+
+        @Test
+        public void palindromeTest() {
+            Assert.assertEquals(true, pp.isPalindrome("heleh"));
+            Assert.assertEquals(true, pp.isPalindrome("h"));
+            Assert.assertEquals(true, pp.isPalindrome("hh"));
+            Assert.assertEquals(false, pp.isPalindrome("ddheleh"));
+            Assert.assertEquals(false, pp.isPalindrome(""));
+        }
+
+        @Test
+        public void test1() {
+            String input = "bb";
+            List<List<String>> output = Arrays.asList(
+                Arrays.asList("b", "b"),
+                Arrays.asList("bb")
+            );
+
+            Assert.assertArrayEquals(
+                output.toArray(),
+                pp.partition(input).toArray()
+            );
+        }
+    }
+}