马拉车模板

Posted 2020-10-09 Roni

Input

输入Str（Str的长度 <= 1000)

Output

输出最长回文子串的长度L。

Input示例

daabaac

Output示例

5

【模板】

#include<cstdio>  
#include<cstring>  
#include<algorithm>  
using namespace std;  
char ch[100100];  
char T[200200];  
int P[200200];  
int main()  
{  
    scanf("%s",ch);  
    int ll=strlen(ch);  
    memset(T,0,sizeof(T));  
    T[0]=1;  
    for (int i=0;i<=ll;i++)  
    {  
        T[2*i+1]=‘#‘;  
        T[2*i+2]=ch[i];  
    }  
    ll=2*ll+2;  
    int ss=0,ans=0,mid;  
    for (int i=1;i<=ll;i++)  
    {  
        if (ss>i)  
        P[i]=min(P[2*mid-i],ss-i+1);  
        else  
        P[i]=1;  
        while (T[i+P[i]]==T[i-P[i]])  
        P[i]++;  
        if (ss<P[i]+i-1)  
        {  
            mid=i;  
            ss=P[i]+i-1;  
        }  
        ans=max(ans,P[i]-1);  
    }  
    printf("%d\n",ans);  
    return 0;  
}  

malache算法

 

#include <cstdio>
#include <iostream>
#include <cstring>
using namespace std;
const int maxn = 100100;
char str[maxn];
char temp[maxn*2];
int l[maxn*2];
void malache(char *str)
{
    int len = strlen(str);
    temp[0]=‘￥‘;
    temp[1]=‘#‘;
    for(int i = 0; i < len ; i++)
    {
        temp[(i+1)*2] = str[i];
        temp[(i+1)*2+1] = ‘#‘;
    }
    int mx = 0, po = 0,ans = 0;
    for(int i = 0;i <= 2*len+1; i++)
    {
        if(i < mx)   l[i] = min(l[2*po-i],mx-i);
        else l[i] = 1;
        while(temp[i-l[i]] == temp[i+l[i]])  l[i]++;
        if(l[i]+i > mx)   {po = i; mx = l[i]+i;}
        ans = max(ans , l[i]);
    }
    cout << ans - 1 <<endl;
}
int main()
{
    memset(temp,0,sizeof(temp));
    cin >> str;
    malache(str);
    return 0;
}

模板2