A.Distinct Split

https://qycode64.com/course/6a47850a69fcccaa3fd46be4/exam/6a60a35d6d83891bb1bc08eb/problem/CF1791D

题意：

思路：

#include<bits/stdc++.h>
using namespace std;
int l[200005],r[200005],v[26];
int main(){
	int t;
	cin>>t;
	while(t--){
		int n;
		string s;
		cin>>n>>s;
		for(int i=0;i<26;i++)v[i]=0;
		l[0]=1;
		v[s[0]-'a']=1;
		for(int i=1;i<n;i++){
			l[i]=l[i-1];
			if(!v[s[i]-'a']){
				v[s[i]-'a']=1;
				l[i]++;
			}
		}
		for(int i=0;i<26;i++)v[i]=0;
		r[n-1]=1;
		v[s[n-1]-'a']=1;
		for(int i=n-2;i>=0;i--){
			r[i]=r[i+1];
			if(!v[s[i]-'a']){
				v[s[i]-'a']=1;
				r[i]++;
			}
		}
		int ans=0;
		for(int i=0;i<n-1;i++){
			ans=max(ans,l[i]+r[i+1]);
		}
		cout<<ans<<"\n";
	}
	return 0;
}

B.Equivalent Strings

https://qycode64.com/course/6a47850a69fcccaa3fd46be4/exam/6a60a35d6d83891bb1bc08eb/problem/CF559B?lang=zh

题意：

思路：

#include<bits/stdc++.h>
using namespace std;
string zx(string x){
	int n=x.size();
	if(n&1)return x;
	string a=zx(x.substr(0,n/2));
	string b=zx(x.substr(n/2));
	if(a>b)swap(a,b);
	return a+b;
}
int main()
{
	string s,t;
	cin>>s>>t;
	if(zx(s)==zx(t))cout<<"YES";
	else cout<<"NO";
	return 0;
}

C.Password

https://qycode64.com/course/6a47850a69fcccaa3fd46be4/exam/6a60a35d6d83891bb1bc08eb/problem/CF126B?lang=zh

#include<bits/stdc++.h>
using namespace std;
int zx[1000005];
int main(){
	string s;
	cin>>s;
	int n=s.size();
	for(int i=1,j=0;i<n;i++){
		while(j>0&&s[i]!=s[j])j=zx[j-1];
		if(s[i]==s[j])j++;
		zx[i]=j;
	}
	int len=zx[n-1];
	int ans=0;
	while(len>0){
		for(int i=1;i<n-1;i++){
			if(zx[i]==len){
				ans=len;
				break;
			}
		}
		if(ans)break;
		len=zx[len-1];
	}
	if(ans)cout<<s.substr(0,ans);
	else cout<<"Just a legend";
	return 0;
}