476. 数字的补数 - 力扣（LeetCode） (leetcode-cn.com)
此题讲解的是位运算，没有想出来，自己对位运算薄弱
https://blog.csdn.net/zzti_erlie/article/details/80204053?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163229016716780255221358%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=163229016716780255221358&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduend~default-2-80204053.pc_search_all_es&utm_term=java+%3C%3C&spm=1018.2226.3001.4187
以上链接时一个位运算的简单介绍，还要仔细回顾