Submission #1106451

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106451		fatman87878	Necklace (Subtask 1-3) (BOI19_necklace1)	C++17	45 / 85	1558 ms	512 KiB

necklace

#include<bits/stdc++.h>
using namespace std;
#define IOS cin.tie(nullptr)->sync_with_stdio(0),cin.exceptions(cin.failbit);
#define lb(x) (x)&-(x)
#define all(x) (x).begin(),(x).end()
#define ll long long
#define u64 unsigned long long
 
constexpr int maxN=2e5+5;
 
constexpr u64 C = 998244353;
 
string s,t;
 
int a,b;
 
inline bool chk(int guess){
    map<u64,int> hashs;
    u64 hsh=0,x=1;
    for(int i = 0;i<guess-1;i++)x*=C;
    for(int i = 0;i<guess-1;i++)hsh*=C,hsh+=t[i];
    for(int i = guess-1;i<t.size();i++){
        hsh*=C,hsh+=t[i];
        hashs[hsh]=i-guess+1;
        hsh-=x*t[i-guess+1];
    }
    for(int i = 0;i+guess<=s.size();i++){
        u64 fh=0,bh=0;
        for(int j = 0;j<guess;j++)bh*=C,bh+=s[j+i];
        for(int j = 0;j<guess;j++){
            fh*=C;
            fh+=s[j+i];
            bh-=x*s[j+i];
            bh*=C;
            if(hashs.count(fh+bh)){
                a=i,b=hashs[fh+bh];
                return 1;
            }
        }
        u64 fh2=0,bh2=0;
        for(int j = guess;j--;)fh2*=C,fh2+=s[j+i];
        for(int j = guess;j--;){
            bh2*=C;
            bh2+=s[j+i];
            fh2-=x*s[j+i];
            fh2*=C;
            if(hashs.count(fh2+bh2)){
                a=i,b=hashs[fh2+bh2];
                return 1;
            }
        }
    }
    return 0;
}
 
int main(){
    IOS
    cin>>s>>t;
    int l = 0,r = min(s.size(),t.size()),mid;
    for(int i = r;i>=l;i--){
        if(chk(i)){
            return cout<<i<<'\n'<<a<<' '<<b<<'\n',0;
        }
    }
}

Compilation message (stderr)

necklace.cpp: In function 'bool chk(int)':
necklace.cpp:22:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |     for(int i = guess-1;i<t.size();i++){
      |                         ~^~~~~~~~~
necklace.cpp:27:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |     for(int i = 0;i+guess<=s.size();i++){
      |                   ~~~~~~~^~~~~~~~~~
necklace.cpp: In function 'int main()':
necklace.cpp:59:42: warning: unused variable 'mid' [-Wunused-variable]
   59 |     int l = 0,r = min(s.size(),t.size()),mid;
      |                                          ^~~

• Subtask 1: 25 / 25
• Subtask 2: 20 / 20
• Subtask 3: 0 / 40