【Manacher】 HDOJ 3068 最长回文

Manacher学习资料请看http://acm.uestc.edu.cn/bbs/read.php?tid=4294

#include <iostream>  
#include <queue>  
#include <stack>  
#include <map>  
#include <set>  
#include <bitset>  
#include <cstdio>  
#include <algorithm>  
#include <cstring>  
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 300000
#define maxm 300005
#define eps 1e-10
#define mod 1315423911
#define INF 1e17
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid  
#define rson o<<1 | 1, mid+1, R  
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
//LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
// head

char s[maxn], ss[maxn];
int p[maxn], n;

void kp(void)
{
	int id, mx = 0;
	for(int i = 1; i <= n; i++) {
		if(mx > i) p[i] = min(p[2 * id - i], mx - i);
		else p[i] = 1;
		for(; s[i+p[i]] == s[i-p[i]]; p[i]++);
		if(mx < i + p[i]) mx = i + p[i], id = i;
	}
}

void work(void)
{
	int len = strlen(ss), ans = 0;
	s[0] = '$', s[1] = '#';
	for(int i = 0; i < len; i++) s[(i+1)<<1] = ss[i], s[((i+1)<<1) + 1] = '#';
	n = len * 2 + 1, kp();
	s[n+1] = 0;
	for(int i = 1; i <= n; i++) ans = max(ans, p[i] - 1);
	printf("%d\n", ans);
}

int main(void)
{
	while(scanf("%s", ss)!=EOF) work();
	return 0;
}