leetcode/solutions/ValidParentheses.java at main · Andre-PI/leetcode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72

/*20. Valid Parentheses
leetcode link: https://leetcode.com/problems/valid-parentheses/description/
Solved
Easy
Topics
Companies
Hint
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Every close bracket has a corresponding open bracket of the same type.


Example 1:

Input: s = "()"
Output: true
Example 2:

Input: s = "()[]{}"
Output: true
Example 3:

Input: s = "(]"
Output: false


Constraints:

1 <= s.length <= 104
s consists of parentheses only '()[]{}'.


Accepted
Solution
Runtime 1ms
Beats 98.66% of users with Java

Memory
41.43 MB
Beats
46.12%
of users with Java
*/
import java.util.Stack;

public class ValidParentheses {

    Stack<Character> stack = new Stack<>();

    public boolean isValid(String s) {
        for (char value : s.toCharArray()) {
            if (value == '(' || value == '[' || value == '{') {
                stack.push(value);
            } else {
                if (stack.empty() ||
                        value == ')' && stack.peek() != '(' ||
                        value == ']' && stack.peek() != '[' ||
                        value == '}' && stack.peek() != '{') {
                    return false;
                } else {
                    stack.pop();
                }
            }
        }
        return stack.empty();
    }
}