题目链接
题解链接

解题思路

• 经典约瑟夫环 plus 经典记忆化搜索技巧
• \(f(n,m)=\begin{cases}0 & (n=0)\\ [f(n-1,m)+m]\%n&(n>0)\end{cases}\)

代码

class Solution {
public:
    struct pair_hash {
        inline size_t operator()(const pair<int,int>&p)const{
            return (((unsigned)p.first<<17)+p.second);
        }
    };

    unordered_map<pair<int,int>,int,pair_hash>josephus;
    int lastRemaining(int n, int m) {
        auto state=make_pair(n,m);
        if(josephus[state])return josephus[state];
        return josephus[state]=(n?(lastRemaining(n-1,m)+m)%n:1);
    }
};