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
class Solution {
public boolean isValid(String s) {
int l = s.length();
if(l == 0){
return true;
}
if(l % 2 != 0){
return false;
}
Stack<Character> stack = new Stack<>();
for(int i = 0;i < l;i++){
Character c = s.charAt(i);
if(stack.isEmpty()){
stack.push(c);
}else{
Character cc = stack.pop();
if(!match(cc,c)){
stack.push(cc);
stack.push(c);
}
}
}
if(stack.empty()){
return true;
}
return false;
}
public boolean match(Character c, Character cc){
if(c.equals('(') && cc.equals(')')){
return true;
}
if(c.equals('[') && cc.equals(']')){
return true;
}
if(c.equals('{') && cc.equals('}')){
return true;
}
return false;
}
}