1754. 构造字典序最大的合并字符串

1754. 构造字典序最大的合并字符串

题解：
每次从word1 和 word2 中取首字符 添加到merge字符串中，使得merge字符串字典序最大

1. 比较word1 和 word2 的首字符，谁大用谁的
2. 如果word1 和 word2 的首字符相等，此时需要比较word1 和 word2的字典序谁大，优先取字典序大的那个

class Solution {
    public String largestMerge(String word1, String word2) {
        int l1 = word1.length();
        int l2 = word2.length();
        char[] res = new char[l1 + l2];
        char[] w1 = word1.toCharArray();
        char[] w2 = word2.toCharArray();
        int i = 0, j = 0, k = 0;
        while (i < l1 && j < l2) {
            if (w1[i] > w2[j]) res[k++] = w1[i++];
            else if (w1[i] < w2[j]) {
                res[k++] = w2[j++];
            } else {
                if (word1.substring(i).compareTo(word2.substring(j)) > 0) {
                    res[k++] = w1[i++];
                } else {
                    res[k++] = w2[j++];
                }
            } ;
        }
        while (i < l1) res[k++] = w1[i++];
        while (j < l2) res[k++] = w2[j++];
        return new String(res);
    }
}