Codeforces Round #648 (Div. 2)--C. Rotation Matching

After the mysterious disappearance of Ashish, his two favourite disciples Ishika and Hriday, were each left with one half of a secret message. These messages can each be represented by a permutation of size n. Let’s call them a and b.

Note that a permutation of n elements is a sequence of numbers a1,a2,…,an, in which every number from 1 to n appears exactly once.

The message can be decoded by an arrangement of sequence a and b, such that the number of matching pairs of elements between them is maximum. A pair of elements ai and bj is said to match if:

i=j, that is, they are at the same index.
ai=bj
His two disciples are allowed to perform the following operation any number of times:

choose a number k and cyclically shift one of the permutations to the left or right k times.
A single cyclic shift to the left on any permutation c is an operation that sets c1:=c2,c2:=c3,…,cn:=c1 simultaneously. Likewise, a single cyclic shift to the right on any permutation c is an operation that sets c1:=cn,c2:=c1,…,cn:=cn−1 simultaneously.

Help Ishika and Hriday find the maximum number of pairs of elements that match after performing the operation any (possibly zero) number of times.

Input
The first line of the input contains a single integer n (1≤n≤2⋅105) — the size of the arrays.

The second line contains n integers a1, a2, …, an (1≤ai≤n) — the elements of the first permutation.

The third line contains n integers b1, b2, …, bn (1≤bi≤n) — the elements of the second permutation.

Output
Print the maximum number of matching pairs of elements after performing the above operations some (possibly zero) times.

Examples
inputCopy
5
1 2 3 4 5
2 3 4 5 1
outputCopy
5
inputCopy
5
5 4 3 2 1
1 2 3 4 5
outputCopy
1
inputCopy
4
1 3 2 4
4 2 3 1
outputCopy
2
Note
For the first case: b can be shifted to the right by k=1. The resulting permutations will be {1,2,3,4,5} and {1,2,3,4,5}.

For the second case: The operation is not required. For all possible rotations of a and b, the number of matching pairs won’t exceed 1.

For the third case: b can be shifted to the left by k=1. The resulting permutations will be {1,3,2,4} and {2,3,1,4}. Positions 2 and 4 have matching pairs of elements. For all possible rotations of a and b, the number of matching pairs won’t exceed 2.
题意：给你两个数组 ，每个数组元素不重复，可以平移b数组，让a b 数组 相同位置上相等的数最多。
思路：当时在做的时候 想暴力肯定是不行，肯定有一些技巧，太可惜了，
要利用好 数组不重复，先以c[a[i]]=i;这样来存位置，之后在b数组中,平移的距离dis=c[b[i]]-i;当然可能为负，为负就加n，然后 你以距离为角标 让d[dis]++;
因为平移距离一样说明相等的数就多呗

#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
#define inf 0x3f3f3f3f3f;
typedef long long ll;
int a[210000], b[210000];
int c[210000];
int d[210000];
int main()
{
	
		memset(a, 0, sizeof a);
		memset(b, 0, sizeof b);	memset(c, 0, sizeof c);	memset(d, 0, sizeof d);
		int n; cin >> n;
		for (int i = 1; i <= n; i++)
		{
			cin >> a[i];
			c[a[i]] = i;
		}
		for (int i = 1; i <= n; i++)
		{
			cin >> b[i];
			int u = c[b[i]]-i;
			if (u < 0)
				u = n + u;
			d[u]++;
		}
		int maxx = 0;
		for (int i = 0; i <= n; i++)
		{
			maxx = max(maxx, d[i]);
		}
		cout << maxx << endl;
	

}