【BZOJ4391】[Usaco2015 dec]High Card Low Card(貪心)
阿新 • • 發佈:2018-10-04
pac 前綴 ble cstring cst getc getch end !=
【BZOJ4391】[Usaco2015 dec]High Card Low Card(貪心)
題面
BZOJ
題解
預處理前綴後綴的結果,中間找個地方合並就好了。
#include<iostream> #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<algorithm> #include<set> using namespace std; #define MAX 100100 inline int read() { int x=0;bool t=false;char ch=getchar(); while((ch<'0'||ch>'9')&&ch!='-')ch=getchar(); if(ch=='-')t=true,ch=getchar(); while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar(); return t?-x:x; } int a[MAX],b[MAX],n,tot,ans; bool vis[MAX]; int s1[MAX],s2[MAX]; set<int> S; int main() { n=read(); for(int i=1;i<=n;++i)vis[a[i]=read()]=true; for(int i=1;i<=n+n;++i)if(!vis[i])b[++tot]=i; for(int i=1;i<=n;++i)S.insert(b[i]); for(int i=1;i<=n;++i) { set<int>::iterator it=S.upper_bound(a[i]); if(it!=S.end())s1[i]=s1[i-1]+1,S.erase(it); else s1[i]=s1[i-1]; } S.clear(); for(int i=1;i<=n;++i)S.insert(-b[i]); for(int i=n;i;--i) { set<int>::iterator it=S.upper_bound(-a[i]); if(it!=S.end())s2[i]=s2[i+1]+1,S.erase(it); else s2[i]=s2[i+1]; } for(int i=0;i<=n;++i)ans=max(ans,s1[i]+s2[i+1]); printf("%d\n",ans); return 0; }
【BZOJ4391】[Usaco2015 dec]High Card Low Card(貪心)