构造 Codeforces Round #310 (Div. 2) B. Case of Fake Numbers

题目传送门

/*
    题意：n个数字转盘，刚开始每个转盘指向一个数字(0~n-1，逆时针排序)，然后每一次转动，奇数的+1，偶数的-1，问多少次使第i个数字转盘指向i-1
    构造：先求出使第1个指向0要多少步，按照这个次数之后的能否满足要求
    题目读的好累:(
*/
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;

const int MAXN = 1e3 + 10;
const int INF = 0x3f3f3f3f;
int a[MAXN];

int main(void)      //Codeforces Round #310 (Div. 2) B. Case of Fake Numbers
{
    // freopen ("B.in", "r", stdin);

    int n;
    while (scanf ("%d", &n) == 1)
    {
        for (int i=1; i<=n; ++i)    scanf ("%d", &a[i]);
        int cnt = 0;
        if (a[1] != 0)
        {
            cnt = (n - 1) - a[1] + 1;
        }

        bool flag = true;
        for (int i=2; i<=n; ++i)
        {
            if (i & 1)
            {
                for (int j=1; j<=cnt; ++j)
                {
                    a[i]++;
                    if (a[i] == n)    a[i] = 0;
                }
                if (a[i] != i - 1)    {flag = false;    break;}
            }
            else
            {
                for (int j=1; j<=cnt; ++j)
                {
                    a[i]--;
                    if (a[i] == -1)    a[i] = n - 1;
                }
                if (a[i] != i - 1)    {flag = false;    break;}
            }
        }

        (flag) ? puts ("Yes") : puts ("No");
    }

    return 0;
}