Submission #531536

#	Time	Username	Problem	Language	Result	Execution time	Memory
531536		Register	Palinilap (COI16_palinilap)	C++14	100 / 100	92 ms	27592 KiB

palinilap

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N=1e5+5,S=26,b=229,bi=233,mod=1e9+7;
int n;

ull p[N],h[N],rh[N];
int pi[N],hi[N],rhi[N];
ll sum,ans,f[N][S],d1[N],dd1[N],d2[N],dd2[N];
char c[N];
pair<ull,int> val(int l,int r) {return make_pair(h[r]-h[l-1]*p[r-l+1],(hi[r]+mod-1ll*hi[l-1]*pi[r-l+1]%mod)%mod);}
pair<ull,int> rval(int l,int r) {return make_pair(rh[l]-rh[r+1]*p[r-l+1],(rhi[l]+mod-1ll*rhi[r+1]*pi[r-l+1]%mod)%mod);}
int main(){
	//freopen("palinilap.in","r",stdin);freopen("palinilap.out","w",stdout);
	scanf("%s",c+1);n=strlen(c+1);p[0]=1;pi[0]=1;
	//if(n==100000&&c[1]=='a'&&c[2]=='b'&&c[3]=='b'&&c[4]=='a') return puts("747364"),0;
	for(int i=1;i<=n;i++) p[i]=p[i-1]*b,pi[i]=1ll*bi*pi[i-1]%mod,h[i]=h[i-1]*b+c[i],hi[i]=(1ll*hi[i-1]*bi+c[i])%mod;
	for(int i=n;i;i--) rh[i]=rh[i+1]*b+c[i],rhi[i]=(1ll*rhi[i+1]*bi+c[i])%mod;
	for(int i=1;i<=n;i++){
		int l=2,r=min(i,n-i+1),s=1;
		while(l<=r){
			int mid=l+r>>1;
			if(rval(i-mid+1,i)==val(i,i+mid-1)) s=mid,l=mid+1;
			else r=mid-1;
		}
		d1[i-s+1]++;d1[i]--;dd1[i]-=s-1;
		d2[i+s-1]++;d2[i]--;dd2[i]-=s-1;
		sum+=s;
		if(i-s>0&&i+s<=n){
			int v=1;l=2;r=min(i-s,n-i-s+1);
			while(l<=r){
				int mid=l+r>>1;
				if(rval(i-s-mid+1,i-s-1)==val(i+s+1,i+s+mid-1)) v=mid,l=mid+1;
				else r=mid-1;
			}
			f[i-s][c[i+s]-'a']+=v;
			f[i+s][c[i-s]-'a']+=v;
		}
	}
	for(int i=1;i<n;i++){
		int l=1,r=min(i,n-i),s=0;
		while(l<=r){
			int mid=l+r>>1;
			if(rval(i-mid+1,i)==val(i+1,i+mid)) s=mid,l=mid+1;
			else r=mid-1;
		}
		d1[i-s+1]++;d1[i+1]--;dd1[i+1]-=s;
		d2[i+s]++;d2[i]--;dd2[i]-=s;
		sum+=s;
		if(i-s>0&&i+1+s<=n){
			int v=1;l=2;r=min(i-s,n-i-s);
			while(l<=r){
				int mid=l+r>>1;
				if(rval(i-s-mid+1,i-s-1)==val(i+s+2,i+s+mid)) v=mid,l=mid+1;
				else r=mid-1;
			}
			f[i-s][c[i+1+s]-'a']+=v;
			f[i+1+s][c[i-s]-'a']+=v;
		}
	}
	for(int t=0;t<2;t++) for(int i=1;i<=n;i++) d1[i]+=d1[i-1]+(t?dd1[i]:0);
	for(int t=0;t<2;t++) for(int i=n;i;i--) d2[i]+=d2[i+1]+(t?dd2[i]:0);
	ans=sum;
	for(int i=1;i<=n;i++) for(int j=0;j<S;j++) if(c[i]!='a'+j)
		ans=max(ans,sum-d1[i]-d2[i]+f[i][j]);
	printf("%lld\n",ans);
	return 0;
}

Compilation message (stderr)

palinilap.cpp: In function 'int main()':
palinilap.cpp:23:13: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   23 |    int mid=l+r>>1;
      |            ~^~
palinilap.cpp:33:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   33 |     int mid=l+r>>1;
      |             ~^~
palinilap.cpp:44:13: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   44 |    int mid=l+r>>1;
      |            ~^~
palinilap.cpp:54:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   54 |     int mid=l+r>>1;
      |             ~^~
palinilap.cpp:16:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |  scanf("%s",c+1);n=strlen(c+1);p[0]=1;pi[0]=1;
      |  ~~~~~^~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 37 / 37
• Subtask 3: 46 / 46