递归写法

class Solution {
public:
    int lastRemaining(int n, int m){
        if (n == 1) return 0;
        return (lastRemaining(n - 1, m) + m) % n;
    }
};

迭代写法

class Solution {
public:
    int lastRemaining(int n, int m){
        if (n == 1) return 0;
        int ret = 0;
        for (int i = 1; i < n;) {
            i ++ ;
            ret = (ret + m) % i;
        }
        return ret;
    }
};