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

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

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

     return ;
 }