Leetcode: 20. Valid Parentheses
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
Solution:
class Solution {
public boolean isValid(String s) {
char[] pars = s.toCharArray();
Stack<Character> stack = new Stack<>();
for(char par:pars){
//the difference of ( and ) is 1, { } and [ ] are 2
if(stack.size() >0 && ((par-stack.peek()==1)||(par-stack.peek())==2))
stack.pop();
else
stack.add(par);
}
return stack.size() == 0;
}
}
