ncpc2014-Clock Pictures

Clock Pictures

kmp

#include<bits/stdc++.h>
using namespace std;
const int maxn=2*1e5+10;
int s[maxn],t[maxn];
int s1[2*maxn],t1[maxn];
int Next[maxn];
int n;
void get_Next()
{//Next数组保存了以i结尾的字符串的最长公共前缀和后缀的起始坐标
    int i,j;
    Next[0] = j = -1;
    i = 0;
    while(i < n)
    {
        while(j!=-1&&t1[j]!=t1[i])//自身和自身进行匹配
            j = Next[j];
        Next[++i] = ++j;
    }
}
int kmp()
{
    int i,j;
    i = j = 0;
    int l1=2*n;
    int l2=n;
    while(i < l1&&j<l2)
    {
       if(j==-1||s1[i]==t1[j])
        {
            i++;j++;
        }
        else
            j=Next[j];

    }
    if(j == l2)
        return 1;//存在完全匹配状况
    return 0;//不存在匹配情况
}

int main()
{
    //freopen("in.txt", "r", stdin);
    ios::sync_with_stdio(false);
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> s[i];
    for(int i=0; i<n; i++)
        cin>>t[i];
    sort(s, s + n);
    sort(t, t + n);
    for (int i = 1; i < n; i++)
    {
        s1[i - 1] = s[i] - s[i - 1];

    }
     for (int i = 1; i < n; i++)
    {

        t1[i - 1] = t[i] - t[i - 1];
    }
    s1[n - 1] = 360000 + s[0] - s[n - 1];
    t1[n - 1] = 360000 + t[0] - t[n - 1];
    for (int i = 0; i < n; i++) s1[i + n] = s1[i];
    get_Next();
    bool flag =kmp();
    if (flag)
        cout << "possible" << endl;
    else
        cout << "impossible" << endl;
    return 0;
}