When you see an opening bracket, you need to remember it so you can match it with a closing bracket later. What data structure remembers things in "most recent first" order? A stack. Push opening brackets onto the stack. When you see a closing bracket, check if it matches the most recent opening bracket (top of stack).
##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######
$ curl repovive.com/roadmaps/maang-interview-prep/stacks/valid-parentheses-hint
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