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题意:给你一个字符串,然后让你输出这个串的最长回文子串的长度。
思路:马拉车模板题。
AC Code:
#include<iostream>
#include<cstring>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<cstdio>
#include<iomanip>
#include<sstream>
#include<algorithm>
using namespace std;
#define read(x) scanf("%d",&x)
#define Read(x,y) scanf("%d%d",&x,&y)
#define sRead(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define gc(x) scanf(" %c",&x);
#define mmt(x,y) memset(x,y,sizeof x)
#define write(x) printf("%d\n",x)
#define INF 0x3f3f3f3f
#define ll long long
#define mod 998244353
#define pdd pair<double,double>
const int N = 1000;
const int M= 1e6+5;
char Ma[M];
int Mp[M];
void Manacher(char s[],int len){
int l = 0;
Ma[l++] = '$';
Ma[l++] = '#';
for(int i =0;i < len;++i){
Ma[l++] = s[i];
Ma[l++] = '#';
}
Ma[l ] = 0;
int mx = 0,id = 0;
for(int i = 0;i < l;++i){
Mp[i] = mx > i ? min(Mp[2*id - i],mx - i):1;
while(Ma[i + Mp[i]] == Ma[i - Mp[i]]) Mp[i]++;
if(i + Mp[i] > mx){
mx = i + Mp[i];
id = i;
}
}
}
char s[M];
int main()
{
while(scanf("%s",s) == 1){
int len = strlen(s);
Manacher(s,len);
int ans = 0;
for(int i = 0;i < 2*len +2; ++i){
ans = max(ans,Mp[i] - 1);
}
cout<<ans<<endl;
}
}