diff --git a/src/main/java/com/thealgorithms/strings/ValidParentheses.java b/src/main/java/com/thealgorithms/strings/ValidParentheses.java
index 629fee495d84..25a72f379dec 100644
--- a/src/main/java/com/thealgorithms/strings/ValidParentheses.java
+++ b/src/main/java/com/thealgorithms/strings/ValidParentheses.java
@@ -1,59 +1,53 @@
package com.thealgorithms.strings;
-// Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine
-// if the input string is valid. An input string is valid if: Open brackets must be closed by
-// the same type of brackets. Open brackets must be closed in the correct order. Every close
-// bracket has a corresponding open bracket of the same type.
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Map;
+
+/**
+ * Validates if a given string has valid matching parentheses.
+ *
+ * A string is considered valid if:
+ *
+ * - Open brackets are closed by the same type of brackets.
+ * - Brackets are closed in the correct order.
+ * - Every closing bracket has a corresponding open bracket of the same type.
+ *
+ *
+ * Allowed characters: '(', ')', '{', '}', '[', ']'
+ */
public final class ValidParentheses {
private ValidParentheses() {
}
+
+ private static final Map BRACKET_PAIRS = Map.of(')', '(', '}', '{', ']', '[');
+
+ /**
+ * Checks if the input string has valid parentheses.
+ *
+ * @param s the string containing only bracket characters
+ * @return true if valid, false otherwise
+ * @throws IllegalArgumentException if the string contains invalid characters or is null
+ */
public static boolean isValid(String s) {
- char[] stack = new char[s.length()];
- int head = 0;
+ if (s == null) {
+ throw new IllegalArgumentException("Input string cannot be null");
+ }
+
+ Deque stack = new ArrayDeque<>();
+
for (char c : s.toCharArray()) {
- switch (c) {
- case '{':
- case '[':
- case '(':
- stack[head++] = c;
- break;
- case '}':
- if (head == 0 || stack[--head] != '{') {
- return false;
- }
- break;
- case ')':
- if (head == 0 || stack[--head] != '(') {
- return false;
- }
- break;
- case ']':
- if (head == 0 || stack[--head] != '[') {
+ if (BRACKET_PAIRS.containsValue(c)) {
+ stack.push(c); // opening bracket
+ } else if (BRACKET_PAIRS.containsKey(c)) {
+ if (stack.isEmpty() || stack.pop() != BRACKET_PAIRS.get(c)) {
return false;
}
- break;
- default:
- throw new IllegalArgumentException("Unexpected character: " + c);
- }
- }
- return head == 0;
- }
- public static boolean isValidParentheses(String s) {
- int i = -1;
- char[] stack = new char[s.length()];
- String openBrackets = "({[";
- String closeBrackets = ")}]";
- for (char ch : s.toCharArray()) {
- if (openBrackets.indexOf(ch) != -1) {
- stack[++i] = ch;
} else {
- if (i >= 0 && openBrackets.indexOf(stack[i]) == closeBrackets.indexOf(ch)) {
- i--;
- } else {
- return false;
- }
+ throw new IllegalArgumentException("Unexpected character: " + c);
}
}
- return i == -1;
+
+ return stack.isEmpty();
}
}
diff --git a/src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java b/src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java
index 2b6884c91c8f..23d41b159fe2 100644
--- a/src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java
+++ b/src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java
@@ -1,27 +1,15 @@
package com.thealgorithms.strings;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
public class ValidParenthesesTest {
- @Test
- void testOne() {
- assertTrue(ValidParentheses.isValid("()"));
- assertTrue(ValidParentheses.isValidParentheses("()"));
- }
-
- @Test
- void testTwo() {
- assertTrue(ValidParentheses.isValid("()[]{}"));
- assertTrue(ValidParentheses.isValidParentheses("()[]{}"));
- }
-
- @Test
- void testThree() {
- assertFalse(ValidParentheses.isValid("(]"));
- assertFalse(ValidParentheses.isValidParentheses("(]"));
+ @ParameterizedTest(name = "Input: \"{0}\" → Expected: {1}")
+ @CsvSource({"'()', true", "'()[]{}', true", "'(]', false", "'{[]}', true", "'([{}])', true", "'([)]', false", "'', true", "'(', false", "')', false"})
+ void testIsValid(String input, boolean expected) {
+ assertEquals(expected, ValidParentheses.isValid(input));
}
}
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