判断链表是否合并

  public String findMergeNode(List<String> aList, List<String> bList) {
        List<String> longList;
        List<String> shortList;
        int offset = 0;
        String mergeNode = null;
        if (aList.size() > bList.size()) {
            longList = aList;
            shortList = bList;
            offset = aList.size() - bList.size();
        } else {
            longList = bList;
            shortList = aList;
            offset = bList.size() - aList.size();
        }
        for (int i = 0; i < longList.size() - offset; i++) {
            String a = shortList.get(i);
            String b = longList.get(i + offset);
            if (a == b) {
                if (mergeNode == null) {
                    mergeNode = a;
                }
            } else {
                mergeNode = null;
            }
        }
        return mergeNode;
    }