整理的算法模板：ACM算法模板總結（分類詳細版）
C. Hilbert's Hotel
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Hilbert's Hotel is a very unusual hotel since the number of rooms is infinite! In fact, there is exactly one room for every integer, including zero and negative integers. Even stranger, the hotel is currently at full capacity, meaning there is exactly one guest in every room. The hotel's manager, David Hilbert himself, decides he wants to shuffle the guests around because he thinks this will create a vacancy (a room without a guest).
For any integer kk and positive integer nn, let kmodnkmodn denote the remainder when kk is divided by nn. More formally, r=kmodnr=kmodn is the smallest non-negative integer such that k−rk−r is divisible by nn. It always holds that 0≤kmodn≤n−10≤kmodn≤n−1. For example, 100mod12=4100mod12=4 and (−1337)mod3=1(−1337)mod3=1.
Then the shuffling works as follows. There is an array of nn integers a0,a1,…,an−1a0,a1,…,an−1. Then for each integer kk, the guest in room kk is moved to room number k+akmodnk+akmodn.
After this shuffling process, determine if there is still exactly one guest assigned to each room. That is, there are no vacancies or rooms with multiple guests.
Input
Each test consists of multiple test cases. The first line contains a single integer tt (1≤t≤1041≤t≤104) — the number of test cases. Next 2t2t lines contain descriptions of test cases.
The first line of each test case contains a single integer nn (1≤n≤2⋅1051≤n≤2⋅105) — the length of the array.
The second line of each test case contains nn integers a0,a1,…,an−1a0,a1,…,an−1 (−109≤ai≤109−109≤ai≤109).
It is guaranteed that the sum of nn over all test cases does not exceed 2⋅1052⋅105.
Output
For each test case, output a single line containing "YES" if there is exactly one guest assigned to each room after the shuffling process, or "NO" otherwise. You can print each letter in any case (upper or lower).
Example
input
Copy
6 1 14 2 1 -1 4 5 5 5 1 3 3 2 1 2 0 1 5 -239 -2 -100 -3 -11
output
Copy
YES YES YES NO NO YES
Note
In the first test case, every guest is shifted by 1414 rooms, so the assignment is still unique.
In the second test case, even guests move to the right by 11 room, and odd guests move to the left by 11 room. We can show that the assignment is still unique.
In the third test case, every fourth guest moves to the right by 11 room, and the other guests move to the right by 55 rooms. We can show that the assignment is still unique.
In the fourth test case, guests 00 and 11 are both assigned to room 33.
In the fifth test case, guests 11 and 22 are both assigned to room 22.
題意
現在有很多顧客編號爲【0，正無窮】，再給出一個數組An；然後對於每一個顧客k，把它移到 第(k+a[k%n]）的房間；
然後判斷不會出現有一個房間存在兩個人，轉化一下題意就是：
對於非負整數k (0 <= k <= +∞)，對k做 (k+a[k%n]）的變換，判斷變換後是否會出現相同的數字；
可以發現只要0~n-1之內的k變換後沒有出現相同的數字，那麼大於k的數字變換後也不會出現相同的數字；所以只需要對 0 ~ n-1的數進行模擬即可；
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=2*1e5;
int a[N];
unordered_map<int,int> mp;
int main()
{
int t;
cin >>t;
while(t--)
{
mp.clear();
int flag=1;
int n;
cin >>n;
for(int i=0;i<n;i++) cin >>a[i];
for(int i=0;i<n;i++)
{
int x=((i+a[i])%n+n)%n;
if(mp[x])
{
flag=0;
break;
}
mp[x]++;
}
if(flag) puts("YES");
else puts("NO");
}
}