Overview
Valid Parentheses: check karo ()، []، {} string mein properly matched aur nested hain.
Analogy
Jaise ledger ka zero balance—har withdrawal (closing) ke liye corresponding deposit (opening) chahiye.
Step-by-step
- Stack aur matching map use karo
- Opening brackets stack mein push karo
- Closing bracket stack top se compare karo
- End mein stack khaali hai toh valid
Visual
"({[]})" → stack:( { [ → ] match→}match→)match→empty=True
"(]" → ) ke baad ] → ( se match nahi=False
Common mistakes
- Khaali string invalid maanna (yeh valid hai)
- End mein stack khaali check karna bhool jana
Practice questions
- Valid banane ke liye minimum additions/deletions nikalo
- Longest valid parentheses substring nikalo