hiho 第1周 最长回文子串

#include <bits/stdc++.h>
using namespace std;

bool table[10000][10000] = {false};

string longestPalindromeDP(string s)
{
    int n = s.length();
    int longestBegin = 0;
    int maxLen = 1;
    memset(table,0,sizeof(table));
    for (int i = 0; i < n; i++)
        table[i][i] = true;   //前期的初始化


    for (int len = 2; len <= n; len++)
    {
        for (int i = 0; i < n-len+1; i++)
        {
            int j = i+len-1;
            if (s[i] == s[j] && table[i+1][j-1])
            {
                table[i][j] = true;
                longestBegin = i;
                maxLen = len;
            }
        }
    }
    return s.substr(longestBegin, maxLen);
}

int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        string str;
        cin>>str;
        string ans = longestPalindromeDP(str);
        cout<<ans.length()<<endl;
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

const int maxn = 1000008;

char instr[maxn],str[maxn*2];
int rad[maxn*2];


int Manacher()
{
    int i,j,maxx;
    int n = strlen(instr);
    memset(str,‘#‘,sizeof(str));
    for(i=0;i<n;i++)
        str[(i+1)<<1] = instr[i];

    n = (n+1)<<1;
    str[n] = ‘$‘;
    int maxRad;
    maxRad = j = maxx = 0;
    for(i = 0;i<n;i++)
    {
        if(i<maxx)
            rad[i] = min(rad[2*j-i],maxx-i);
        else rad[i] = 1;

        while(str[i-rad[i]]==str[i+rad[i]])
            rad[i] ++;
        if(maxRad<rad[i])
            maxRad = rad[i];
        if(rad[i]+i>maxx)
        {
            j = i;
            maxx = rad[i] + i;
        }

    }
    return maxRad;

}

int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%s",instr);
        printf("%d\n",Manacher()-1);
    }
    return 0;
}