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.
用堆栈思想解决。
import java.util.*;
public class Solution {
public boolean isValid(String s) {
Stack<String> stack = new Stack<String>();
for(int i=0;i<s.length();i++)
{
if(s.charAt(i)=='('||s.charAt(i)=='['||s.charAt(i)=='{')
stack.push(String.valueOf(s.charAt(i)));
else{
if(stack.empty())
{
return false;
}
if(s.charAt(i)==')'){
if(stack.peek().equals("("))
stack.pop();
else
return false;}
else if(s.charAt(i)==']'){
if(stack.peek().equals("["))
stack.pop();
else
return false;}
else if(s.charAt(i)=='}'){
if(stack.peek().equals("{"))
stack.pop();
else
return false;}
}
}
if(stack.empty())
return true;
else
return false;
}
};