LeetCode 20: Valid Parentheses (remastered)

Author: DimkaGorhover

src/main/java/org/gd/leetcode/p0020/Solution.java

@@ -9,6 +9,7 @@
  * @see org.gd.leetcode.p0022.Solution
  * @since 2018-12-29
  */
+@SuppressWarnings("JavadocReference")
 @LeetCode(
         difficulty = LeetCode.Level.EASY,
         tags = {
@@ -17,22 +18,28 @@
         })
 class Solution {
 
-    private static int map(int c) {
-        switch (c) {
-            case ')': return '(';
-            case ']': return '[';
-            case '}': return '{';
-        }
-        return -1;
+    private final byte[] hashTable;
+
+    public Solution() {
+        hashTable = new byte[Byte.MAX_VALUE];
+        hashTable[')'] = '(';
+        hashTable[']'] = '[';
+        hashTable['}'] = '{';
     }
 
     public boolean isValid(String s) {
 
+        if (s == null || s.length() % 2 != 0) {
+            return false;
+        }
+
         int[] stack = new int[s.length()];
 
         int c, mapped, head = 0;
         for (int i = 0; i < s.length(); i++) {
-            if ((mapped = map(c = s.charAt(i))) > 0) {
+            c = s.charAt(i);
+            mapped = hashTable[c];
+            if (mapped > 0) {
                 int top = head <= 0 ? -2 : stack[--head];
                 if (top != mapped)
                     return false;

src/main/java/org/gd/leetcode/p0022/Solution.java

@@ -1,45 +1,53 @@
 package org.gd.leetcode.p0022;
 
+import org.gd.leetcode.common.LeetCode;
+import org.gd.leetcode.common.LeetCode.Level;
+import org.gd.leetcode.common.LeetCode.Tags;
+
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
-import org.gd.leetcode.common.LeetCode;
-import org.gd.leetcode.common.LeetCode.Level;
-import org.gd.leetcode.common.LeetCode.Tags;
-
 /**
  * https://leetcode.com/problems/generate-parentheses/
- * 
+ *
  * Given n pairs of parentheses, write a function to generate all combinations
  * of well-formed parentheses.
- * 
+ *
  * For example, given n = 3, a solution set is:
- * 
+ *
  * [
  *   "((()))",
  *   "(()())",
  *   "(())()",
  *   "()(())",
  *   "()()()"
  * ]
- * 
+ *
  * @author Horkhover Dmytro
  * @see org.gd.leetcode.p0020.Solution
  */
-@LeetCode(difficulty = Level.MEDIUM, tags = { Tags.BACKTRACKING, Tags.STRING })
+@SuppressWarnings("JavadocReference")
+@LeetCode(
+        difficulty = Level.MEDIUM,
+        tags = {
+                Tags.BACKTRACKING,
+                Tags.STRING
+        })
 class Solution {
 
     private List<String> list;
 
     public List<String> generateParenthesis(int n) {
-        if (n <= 0)
+        if (n <= 0) {
             return Collections.emptyList();
+        }
 
-        if (n == 1)
+        if (n == 1) {
             return Arrays.asList("()");
+        }
 
         list = new ArrayList<>();
         byte[] chars = new byte[n << 1];

src/test/java/org/gd/leetcode/p0020/SolutionTest.java

@@ -1,13 +1,14 @@
 package org.gd.leetcode.p0020;
 
-import org.junit.jupiter.api.*;
+import lombok.NonNull;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 
 import java.util.stream.Stream;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
  * Test for {@link Solution};
@@ -17,11 +18,14 @@
  */
 class SolutionTest {
 
+    @NonNull
     private static Stream<Arguments> args() {
+        String longTestCase0 = "[([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([()])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])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         return Stream.of(
                 Arguments.of("()[]{", false),
                 Arguments.of("{[]}", true),
-                Arguments.of("([)]", false)
+                Arguments.of("([)]", false),
+                Arguments.of(longTestCase0, true)
         );
     }