public class ValidParentheses{
    public boolean isValid(String s) {
        Stack<Character> stack= new Stack<Character>();
        for(char c:s.toCharArray()){
            if(c=='(')
                stack.push(')');
           else if(c=='[')
                stack.push(']');
           else if(c=='{')
                stack.push('}');
            else if(stack.isEmpty()||stack.pop()!=c)
                return false;
            
            
            
        }
        
        return stack.isEmpty();
        

    }
}

Starzhang
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