forked from rpj911/LeetCode_algorithm
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathIsValid.java
More file actions
81 lines (72 loc) · 2.24 KB
/
IsValid.java
File metadata and controls
81 lines (72 loc) · 2.24 KB
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
package Algorithms.stack;
import java.util.Stack;
public class IsValid {
public boolean isValid1(String s) {
if (s == null || s.length() == 0) {
return true;
}
Stack<Character> stack = new Stack<Character>();
int len = s.length();
for (int i = 0; i < len; i++) {
char c = s.charAt(i);
if (stack.isEmpty()) {
if (c == ']' || c == ')' || c == '}') {
return false;
}
stack.push(c);
continue;
}
if (c == ')' && stack.peek() == '('
|| c == ']' && stack.peek() == '['
|| c == '}' && stack.peek() == '{'
) {
stack.pop();
} else if (c == '(' || c == '[' || c == '{') {
stack.push(c);
} else {
return false;
}
}
return stack.isEmpty();
}
public boolean isValid(String s) {
if (s == null) {
return false;
}
int len = s.length();
// bug 1: don't use s as the name of the stack.
Stack<Character> stk = new Stack<Character>();
for (int i = 0; i < len; i++) {
char c = s.charAt(i);
switch(c) {
case '(':
case '[':
case '{':
stk.push(c);
break;
case ')':
if (!stk.isEmpty() && stk.peek() == '(') {
stk.pop();
} else {
return false;
}
break;
case '}':
if (!stk.isEmpty() && stk.peek() == '{') {
stk.pop();
} else {
return false;
}
break;
case ']':
if (!stk.isEmpty() && stk.peek() == '[') {
stk.pop();
} else {
return false;
}
break;
}
}
return stk.isEmpty();
}
}