HDU 2203: 亲和串

Posted 2020-10-08

///@date 9/23/2017
///@author Sycamore
///@link http://acm.hdu.edu.cn/showproblem.php?pid=2203
#include<bits/stdc++.h>
using namespace std;
typedef vector<int>VI;
VI getPi(const string& p)
{

   VI pi = VI(p.length());
 int k = -2;
 for (int i = 0; i < p.length(); i++)
   {
      //now k==p[i-1]
 while (k >= -1 && p[k + 1] != p[i])//find pi[i] using pi[i-1]
 k = (k == -1) ? -2 : pi[k];//make shifts
 pi[i] = ++k;
 }
   return pi;
}

bool KMP(const string& t, const string& p)
{
   VI pi = getPi(p);
 int k = -1;
 for (int i = 0; i < t.length(); i++)
   {
      while (k >= -1 && p[k + 1] != t[i])
         k = (k == -1) ? -2 : pi[k];
 k++;
 if (k == p.length() - 1) {
         return true;
 }
   }
   return false;
}

int main()
{

   ios::sync_with_stdio(false);
 cin.tie(nullptr);
 string s,t;
 while(cin>>s>>t)
   {
      s+=s;
 cout<<(KMP(s,t)?"yes\n":"no\n");
 }

}