题解

#pragma GCC optimize(1,"Ofast","inline")
#pragma GCC optimize(2,"Ofast","inline")
#pragma GCC optimize(3,"Ofast","inline")
#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;
struct node{
	int val;
	node *next = nullptr, *pre = nullptr;
};
vector <int> v;
int main(){
	int n, m;
	cin >> n >> m;
	node *head, *r;
	head = new node;
	r = head;
	for(int i = 0; i < n; i++){
		node *p = new node;
		p -> val = i, p -> pre = r;
		r -> next = p;
		r = p;
	}r -> next = head -> next, head -> next -> pre = r;
	node *p = head;
	n--;
	while(n--){
		for(int i = 1; i < m; i++) p = p -> next;
		node *dnode = p -> next;
		dnode -> next -> pre = dnode -> pre, dnode -> pre -> next = dnode -> next;
		delete(dnode);
	}p = p -> next;
	cout << p -> val;

	return 0;
}