LeetCode Entry

20. Valid Parentheses

01.10.2026 easy 2026 kotlin rust

Are braces valid

20. Valid Parentheses easy substack youtube

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Problem TLDR

Are braces valid

Intuition

Push open kind to the stack. Pop close kind if match with top of the stack.

Approach

• or push matching close brace to the stack

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(n)\)

Code

    fun isValid(s: String) = ArrayDeque<Char>().run {
        s.all{if(it in "([{") add(it+1+it.code%2)
            else removeLastOrNull()==it } && isEmpty()}

    pub fn is_valid(s: String) -> bool {
        let mut q = vec![];
        s.bytes().all(|b|if b"([{".contains(&b){q.push(b+1+b%2);true}else{q.pop()==Some(b)})&&q.is_empty()
    }