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Valid Parentheses

Certification: Basic Level Accuracy: 47.96% Submissions: 98 Points: 5

Write a Java program to implement the isValid(String s) function, which determines if an input string containing just the characters '(', ')', '{', '}', '[' and ']' is valid.

Example 1
    

  • Input: s = "()"
    • 

  • Output: true
    • 

  • Explanation:

      

    • Push '(' → Stack = ['(']
      • 

    • Encounter ')' → Matches top, pop '('
      • 

    • Stack is empty → valid
      • 

    

    •
Example 2
    

  • Input: s = "([)]"
    • 

  • Output: false
    • 

  • Explanation:

      

    • Push '(' → Push '['
      • 

    • ')' does not match top '[' → invalid
      • 

    

    •
Constraints
    

  • 1 ≤ s.length ≤ 10^4
    • 

  • s consists of parentheses only '()[]{}'
    • 

  • Time Complexity: O(n)
    • 

  • Space Complexity: O(n)
    •
StringsStackCapgeminiLTIMindtree
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Hint
Solution

Solution Hints

    
  
  • Use a stack to keep track of opening brackets
    • 
  
  • When you encounter an opening bracket, push it onto the stack
    • 
  
  • When you encounter a closing bracket, check if the stack is empty or if the top element is the corresponding opening bracket
    • 
  
  • If the stack is not empty at the end, the string is invalid
    •

Steps to solve by this approach:

 Step 1: Create a stack to store opening brackets.
 Step 2: Iterate through each character in the string.
 Step 3: If the character is an opening bracket ('(', '[', '{'), push it onto the stack.
 Step 4: If the character is a closing bracket (')', ']', '}'), check if the stack is empty.
 Step 5: If stack is not empty, pop the top element and verify it matches the current closing bracket.
 Step 6: If no match or stack is empty, return false.
 Step 7: After processing all characters, return true if stack is empty, false otherwise.

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