_591.java

package com.fishercoder.solutions;

import java.util.ArrayDeque;
import java.util.Deque;

public class _591 {

    public static class Solution1 {

        /**
         * Credit: https://discuss.leetcode.com/topic/91300/java-solution-use-startswith-and-indexof
         */
        public boolean isValid(String code) {
            Deque<String> stack = new ArrayDeque<>();
            for (int i = 0; i < code.length(); ) {
                if (i > 0 && stack.isEmpty()) {
                    return false;
                }
                if (code.startsWith("<![CDATA[", i)) {
                    int j = i + 9;//"<![CDATA[" length is 9
                    i = code.indexOf("]]>", j);
                    if (i < 0) {
                        return false;
                    }
                    i += 3;//"]]>" length is 3
                } else if (code.startsWith("</", i)) {
                    int j = i + 2;
                    i = code.indexOf(">", j);
                    if (i < 0 || i == j || i - j > 9) {
                        return false;
                    }
                    for (int k = j; k < i; k++) {
                        if (!Character.isUpperCase(code.charAt(k))) {
                            return false;
                        }
                    }
                    String s = code.substring(j, i++);
                    if (stack.isEmpty() || !stack.pop().equals(s)) {
                        return false;
                    }
                } else if (code.startsWith("<", i)) {
                    int j = i + 1;
                    i = code.indexOf(">", j);
                    if (i < 0 || i == j || i - j > 9) {
                        return false;
                    }
                    for (int k = j; k < i; k++) {
                        if (!Character.isUpperCase(code.charAt(k))) {
                            return false;
                        }
                    }
                    String s = code.substring(j, i++);
                    stack.push(s);
                } else {
                    i++;
                }
            }
            return stack.isEmpty();
        }
    }

}