bzoj3790: 神奇项链

用manacher搞一搞，然后需要以下区间覆盖的贪心就好了。

#include<bits/stdc++.h>
using namespace std;
char s1[110000],s2[110000];
int n,len,p[110000],lp[110000],rp[110000];
struct one
{
	int x,y;
};
one e[110000];
void manacher()
{
	memset(p,0,sizeof(p));
	int mx=0,id;
	for(int i=1;i<len;i++)
	{
		if(mx>i)p[i]=min(p[id*2-i],mx-i);
		else p[i]=1;
		while(s2[i+p[i]]==s2[i-p[i]])
			p[i]++;
		if(i+p[i]>mx)
			mx=i+p[i],id=i;
	}
}
bool cmp(one aa,one bb)
{return aa.x<bb.x;}
int main()
{
	//freopen("xf.in","r",stdin);
	//freopen("xf.out","w",stdout);
	while(~scanf("%s",s1))
	{
		memset(lp,0,sizeof(lp));
		memset(rp,0,sizeof(rp));
		s2[0]='$';
		n=strlen(s1);
		len=1;
		for(int i=0;i<n;i++)
		{
			s2[len++]='#';
			s2[len++]=s1[i];
		}
		s2[len++]='#';
		manacher();
		for(int i=1;i<len;i++)
		{
			e[i].x=i-p[i]+1;
			e[i].y=i+p[i]-1;
		}
		sort(e+1,e+len,cmp);
		int l=0,r=0,ans=1;
		for(int i=1;i<len;i++)
		{
			if(e[i].x<=rp[ans-1]+1)
			{
				rp[ans]=max(e[i].y,rp[ans]);
				if(rp[ans]==len-1)break;
			}
			else 
			{
				ans++;
				rp[ans]=e[i].y;
			}
		}
		printf("%d\n",ans-1);
	}
	return 0;
}