-
Notifications
You must be signed in to change notification settings - Fork 21
/
_0020_ValidParentheses.java
91 lines (85 loc) · 1.96 KB
/
_0020_ValidParentheses.java
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
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
package leetcode;
import java.util.LinkedList;
/**
* @No 20
* @problem Valid Parentheses
* @level Easy
* @desc 有效的括号
* @author liyazhou
* @date 2017/08
*
* <pre>
* Given a string 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.
* Note that an empty string is also considered valid.
*
* Example 1:
* Input: "()"
* Output: true
*
* Example 2:
* Input: "()[]{}"
* Output: true
*
* Example 3:
* Input: "(]"
* Output: false
*
* Example 4:
* Input: "([)]"
* Output: false
*
* Example 5:
* Input: "{[]}"
* Output: true
* </pre>
*/
public class _0020_ValidParentheses {
/**
* Note
*
* Thought
* 栈
*
* Challenge
*
* Algorithm
* 1.
* 2.
*
* Complexity
* Time,
* Space,
*/
private static class Solution {
public boolean isValid(String s) {
LinkedList<Character> stack = new LinkedList<>();
for (int i = 0; i < s.length(); i ++) {
char ch = s.charAt(i);
if (ch == '(' || ch == '{' || ch == '[') {
stack.push(ch);
}
if (ch == ')') {
if (stack.isEmpty() || stack.pop() != '(') {
return false;
}
}
if (ch == '}') {
if (stack.isEmpty() || stack.pop() != '{') {
return false;
}
}
if (ch == ']') {
if (stack.isEmpty() || stack.pop() != '[') {
return false;
}
}
}
return stack.isEmpty();
}
}
}