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类目归类
[LeetCode 20] Valid Parentheses [Java]
11/23
1. Description
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.
2. Code
import java.util.Stack;
public class LeetCode0020 {
public boolean isValid(String s)
{
if (s == null || s.length() == 0) {
return false;
}
Stack stack = new Stack();
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (!stack.isEmpty()) {
int top = stack.peek();
if (top == '(' && c == ')' || top == '[' && c == ']' || top == '{' && c == '}') {
stack.pop();
}
else {
stack.push(c);
}
}
else if (c == ')' || c == ']' || c == '}') {
return false;
}
else {
stack.push(c);
}
}
return stack.isEmpty();
}
public static void main(String[] args)
{
LeetCode0020 leetcode = new LeetCode0020();
System.out.println(leetcode.isValid("()[]"));
}
}
