poj2081

简单题

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 500004

int f[maxn];
bool vis[maxn * 10];

int main()
{
//    freopen("t.txt", "r", stdin);
    memset(vis, 0, sizeof(vis));
    f[0] = 0;
    for (int i = 1; i < maxn; i++)
    {
        f[i] = f[i - 1] - i > 0  && !vis[f[i - 1] - i]? f[i - 1] - i : f[i - 1] + i;
        vis[f[i]] = true;
    }
    int n;
    while (scanf("%d", &n), n != -1)
        printf("%d\n", f[n]);
    return 0;
}