g0001_0100.s0020_valid_parentheses.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0001_0100.s0020_valid_parentheses;

// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #String #Stack
// #Data_Structure_I_Day_9_Stack_Queue #Udemy_Strings #Big_O_Time_O(n)_Space_O(n)
// #2024_02_11_Time_1_ms_(98.78%)_Space_41.6_MB_(32.59%)

import java.util.Stack;

@SuppressWarnings("java:S1149")
public class Solution {
    public boolean isValid(String s) {
        Stack stack = new Stack<>();
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (c == '(' || c == '[' || c == '{') {
                stack.push(c);
            } else if (c == ')' && !stack.isEmpty() && stack.peek() == '(') {
                stack.pop();
            } else if (c == '}' && !stack.isEmpty() && stack.peek() == '{') {
                stack.pop();
            } else if (c == ']' && !stack.isEmpty() && stack.peek() == '[') {
                stack.pop();
            } else {
                return false;
            }
        }
        return stack.isEmpty();
    }
}