https://www.nowcoder.com/practice/96bd6684e04a44eb80e6a68efc0ec6c5?tpId=13&tqId=11188&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
数组中的逆序对
https://www.cnblogs.com/coffy/p/5896541.html
https://www.nowcoder.com/practice/f78a359491e64a50bce2d89cff857eb6?tpId=13&tqId=11199&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
约瑟夫环
https://www.nowcoder.com/practice/94a4d381a68b47b7a8bed86f2975db46?tpId=13&tqId=11204&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
没怎么看懂
https://www.nowcoder.com/practice/ff05d44dfdb04e1d83bdbdab320efbcb?tpId=13&tqId=11211&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking