[JAVA] solution with HashMap to avoid condition causes

  • 0

    if(s==null || s.length()==0) return true;

        Stack<Character> stack = new Stack<Character>();
        HashMap<Character, Character> map = new HashMap<Character, Character>();
        map.put(')', '(');
        map.put(']', '[');
        map.put('}', '{');
        for(int i=0; i<s.length(); i++) {
            char c = s.charAt(i);
            if(c==')' || c==']' || c=='}') {
                if(stack.isEmpty() || stack.peek()!=map.get(c))  
                    return false;
        return stack.isEmpty();

  • 0

    Did you use the fact that when auto-boxing ASCII chars the Character objects returned for them will be always the same objects? If not see Character.valueOf, and consider using peek().equals( to prevent mismatches for Unicode characters. Same stands for all wrapper classes. Alternatively explicitly unbox both sides: (char)stack.peek()!=(char)map.get(.

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