Valid Parentheses ( Java + Python)

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.

	/*
	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.
	*/
	public class Solution {
	public boolean isValid(String s) {
	if (s==null || s.length()==0){
	return true;
	}
	Stack<Character> checker=new Stack<Character>();
	int i=0;
	while (i<s.length()){
	if (s.charAt(i)=='(' || s.charAt(i)=='[' || s.charAt(i)=='{'){
	checker.push(s.charAt(i));
	i++;
	}
	else if (s.charAt(i)==')' || s.charAt(i)==']' || s.charAt(i)=='}'){
	if (checker.isEmpty()){
	return false;
	}
	else{
	char temp=checker.peek();
	if (isPair(temp, s.charAt(i))){
	checker.pop();
	i++;
	}
	else{
	return false;
	}
	}
	}
	else{
	return false;
	}
	}
	if (checker.isEmpty() ){
	return true;
	}
	return false;
	}
	// check is given two chars are pair
	private boolean isPair(char c1, char c2){
	String validChars="()[]{}";
	int indexC1=validChars.indexOf(c1);
	int indexC2=validChars.indexOf(c2);
	if (indexC1<0||indexC2<0){
	return false;
	}
	if (indexC1+1==indexC2){
	return true;
	}
	return false;
	}
	}

view raw ValidParentheses.java hosted with ❤ by GitHub

	"""
	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.
	"""
	# rewrite at 3/2/2014
	class Solution:
	# @return a boolean
	def isValid(self, s):
	if s==None or len(s)==0:
	return True
	stack=[]
	dict={'}':'{', ']':'[',')':'('}
	for c in s:
	if c=='(' or c=='[' or c=='{':
	stack.append(c)
	elif dict[c]:
	if len(stack)==0:
	return False
	else:
	last=stack[-1]
	if dict[c]!=last:
	return False
	else:
	stack.pop()
	else:
	return False
	return len(stack)==0

view raw ValidParentheses.py hosted with ❤ by GitHub