#02EasyData Structures · 64% acceptance

Valid Bracket Sequence

StackString

Given a string `s` containing only the characters ( ) [ ] { }, determine if the brackets are correctly matched and nested.

Every opening bracket must close in the right order — just like every reagent added must eventually be accounted for.

Examples

Input: s = "()[]{}"

Output: true

Input: s = "([)]"

Output: false

Note: The square bracket closes before the round one it contains.

Constraints

·1 ≤ s.length ≤ 10^4
·s consists only of bracket characters.

Hints

solution.pyPython 3

def is_valid(s):
    pairs = {")": "(", "]": "[", "}": "{"}
    stack = []
    for ch in s:
        if ch in pairs:
            if not stack or stack.pop() != pairs[ch]:
                return False
        else:
            stack.append(ch)
    return not stack

Test console

// hit Run to execute the sample tests

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