CF 2010 C2. Message Transmission Error (hard version) (*1700) 字符串+哈希
题意:
给你一个字符串,让你判断是否是由某个字符串首尾拼接重叠而成的。
思路:
做法很多,最暴力就直接枚举字符串长度,然后哈希即可。
代码:
#include<bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
#define all(u) u.begin(), u.end()
#define endl '\n'
#define debug(x) cout<<#x<<":"<<x<<endl;
typedef pair<int, int> PII;
typedef long long LL;
const int inf = 0x3f3f3f3f;
const int N = 1e5 + 10, M = 105;
const int mod = 1e9 + 7;
const int cases = 0;
struct Hash{
const int mod1=100663319,mod2=201326611;
const LL P1=131,P2=13331;
vector<LL> p1,p2,h1,h2,t1,t2;
void init(string s){
int n=(int)s.size()-1;
p1.assign(n+1,0);p2.assign(n+1,0);
h1.assign(n+1,0);h2.assign(n+1,0);
t1.assign(n+2,0);t2.assign(n+2,0);
p1[0]=p2[0]=1;
for(int i=1;i<=n;i++){
p1[i]=p1[i-1]*P1%mod1;
p2[i]=p2[i-1]*P2%mod2;
h1[i]=(h1[i-1]*P1%mod1+s[i]-'0'+1)%mod1;
h2[i]=(h2[i-1]*P2%mod2+s[i]-'0'+1)%mod2;
}
for(int i=n;i>=1;i--){
t1[i]=(t1[i+1]*P1%mod1+s[i]-'0'+1)%mod1;
t2[i]=(t2[i+1]*P2%mod2+s[i]-'0'+1)%mod2;
}
}
int getHash1(int l,int r){
return (h1[r]-(h1[l-1]*p1[r-l+1])%mod1+mod1)%mod1;
}
int getHash2(int l,int r){
return (h2[r]-(h2[l-1]*p2[r-l+1])%mod2+mod2)%mod2;
}
int getRevHash1(int l,int r){
return (t1[l]-(t1[r+1]*p1[r-l+1])%mod1+mod1)%mod1;
}
int getRevHash2(int l,int r){
return (t2[l]-(t2[r+1]*p2[r-l+1])%mod2+mod2)%mod2;
}
}Hash;
void Showball(){
string s;
cin>>s;
int n=s.size();
s="?"+s;
Hash.init(s);
for(int i=n/2+1;i<n;i++){
if(Hash.getHash1(1,i)==Hash.getHash1(n-i+1,n)&&Hash.getHash2(1,i)==Hash.getHash2(n-i+1,n))
return cout<<"YES\n"<<s.substr(1,i)<<endl,void();
}
cout<<"NO\n";
}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int T=1;
if(cases) cin>>T;
while(T--)
Showball();
return 0;
}
标签:1700,mod1,mod2,const,Transmission,hard,t2,t1,int
From: https://www.cnblogs.com/showball/p/18396483