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

 

 

题目传送门

 1 /*  2  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  3  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  4  题目读的好累:(  5 */  6 #include <cstdio>  7 #include <iostream>  8 #include <algorithm>  9 #include <cstring> 10 #include <cmath> 11 using namespace std; 12 13 const int MAXN = 1e3 + 10; 14 const int INF = 0x3f3f3f3f; 15 int a[MAXN]; 16 17 int main(void) //Codeforces Round #310 (Div. 2) B. Case of Fake Numbers 18 { 19 // freopen ("B.in", "r", stdin); 20 21 int n; 22 while (scanf ("%d", &n) == 1) 23  { 24 for (int i=1; i<=n; ++i) scanf ("%d", &a[i]); 25 int cnt = 0; 26 if (a[1] != 0) 27  { 28 cnt = (n - 1) - a[1] + 1; 29  } 30 31 bool flag = true; 32 for (int i=2; i<=n; ++i) 33  { 34 if (i & 1) 35  { 36 for (int j=1; j<=cnt; ++j) 37  { 38 a[i]++; 39 if (a[i] == n) a[i] = 0; 40  } 41 if (a[i] != i - 1) {flag = false; break;} 42  } 43 else 44  { 45 for (int j=1; j<=cnt; ++j) 46  { 47 a[i]--; 48 if (a[i] == -1) a[i] = n - 1; 49  } 50 if (a[i] != i - 1) {flag = false; break;} 51  } 52  } 53 54 (flag) ? puts ("Yes") : puts ("No"); 55  } 56 57 return 0; 58 }