A：搜索好难啊根本不会啊。
B：暴力枚举给哪段前缀乘，维护一些前后缀最大最小值之类的东西就很好算了。
#include<iostream> #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<algorithm> using namespace std; int read() { int x=0,f=1;char c=getchar(); while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();} while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar(); return x*f; } #define N 1000010 #define ll long long int n,w,v,a[N]; ll ans=-10000000000000000,sum[N],pre[N],suf[N]; int main() { freopen("game.in","r",stdin); freopen("game.out","w",stdout); n=read(),w=-read(),v=-read(); for (int i=1;i<=n;i++) a[i]=read(); for (int i=1;i<=n;i++) sum[i]=sum[i-1]+a[i]; for (int i=1;i<=n+1;i++) pre[i-1]=suf[i]=(sum[n]-sum[i-1])*v+sum[i-1]; for (int i=1;i<=n;i++) pre[i]=max(pre[i],pre[i-1]); for (int i=n;i;i--) suf[i]=min(suf[i],suf[i+1]); for (int i=0;i<=n;i++) ans=max(ans,min(sum[i]*w+suf[i+1]-sum[i],(sum[n]-sum[i])*v+(pre[i]-(sum[n]-sum[i])*v)*w)); cout<<ans; return 0; }
C：吐槽一下这场的心路历程。开场看A，看了一会性质发现转化成了一个2-SAT，这玩意怎么还能计数啊？盯了一个小时一点都不会，暴力都没写就跑了。心态从这就开始崩了。然后半个小时搞掉B。C开始胡乱分析一下觉得某结论很显然，然后写了一个小时差不多搞定了，结果因为各种写挂，大样例跑的比答案大。然而并没有冷静下来去验证结论，并且由于数据范围才50觉得自己肯定假掉了，于是开始退火。退了半天总是比答案小，到处找锅没有任何收获，最后弃疗了连交都没交了。之后调了两个小时才发现做mst时边权开的是int于是炸成负数了。
这个题胡乱分析一下性质跑mst就好了。
#include<iostream> #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<algorithm> #include<ctime> using namespace std; int read() { int x=0,f=1;char c=getchar(); while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();} while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar(); return x*f; } #define N 55 #define T1 1e5 #define T2 1e-8 #define delta 0.98 int n,a[N][N],b[N][N],id[N],id2[N],dfn[N],fa[N],c; long long t[N],u[N],f[N],tmp[N],dis[N][N],ans,tot=1000000000000000; bool cmp(const int&a,const int&b) { return f[a]>f[b]; } struct data { int x,y;long long z; bool operator <(const data&a) const { return z<a.z; } }edge[N*N]; int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);} void SWAP(int x,int y) { swap(id[x],id[y]); dfn[id[x]]=x,dfn[id[y]]=y; } long long getans() { ans=0; for (int i=1;i<=n;i++) fa[i]=i; for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) if (a[i][j]) fa[find(i)]=find(j); for (int i=1;i<=n;i++) { for (int j=1;j<=n;j++) if (a[i][j]) if (dfn[j]<dfn[i]) ans+=u[j]*f[i]*(u[i]-t[i]); else if (dfn[j]>dfn[i]) ans+=t[j]*f[i]*(u[i]-t[i]); ans+=f[i]*((u[i]-1)+t[i])*(u[i]-t[i])>>1; } for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) dis[i][j]=100000000000000000; for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) if (dfn[i]<dfn[j]) { int p=find(i),q=find(j); if (p!=q) dis[p][q]=min(dis[p][q],(t[i]+t[j])*c+t[j]*f[i]*(u[i]-t[i])+u[i]*f[j]*(u[j]-t[j])); } int cnt=0;memset(id2,0,sizeof(id2)); for (int i=1;i<=n;i++) if (find(i)==i) id2[++cnt]=i; int num=0; for (int i=1;i<=cnt;i++) for (int j=1;j<=cnt;j++) num++,edge[num].x=id2[i],edge[num].y=id2[j],edge[num].z=dis[id2[i]][id2[j]]; sort(edge+1,edge+num+1); for (int i=1;i<=n;i++) fa[i]=i; for (int i=1;i<=num;i++) if (find(edge[i].x)!=find(edge[i].y)) ans+=edge[i].z,fa[find(edge[i].x)]=edge[i].y; return ans; } void solve() { double T=T1; long long lastans=tot; while (T>T2) { int x=rand()%(n-1)+1,y=rand()%(n-x)+x+1; SWAP(x,y); ans=getans(); if (ans<lastans||exp((lastans-ans)/T)>1.0*rand()/RAND_MAX) tot=min(tot,ans); else SWAP(x,y),ans=lastans; T*=delta;lastans=ans; } } int main() { freopen("reconstruction.in","r",stdin); freopen("reconstruction.out","w",stdout); n=read();srand(time(0)); for (int i=1;i<=n;i++) t[i]=read(); for (int i=1;i<=n;i++) u[i]=read(); for (int i=1;i<=n;i++) f[i]=read(); if (n==1) {cout<<(f[1]*((u[1]-1)+t[1])*(u[1]-t[1])>>1);return 0;} for (int i=1;i<=n;i++) { for (int j=1;j<=n;j++) { char c=getchar(); while (c!='Y'&&c!='N') c=getchar(); if (c=='Y') a[i][j]=1; } } c=read(); for (int i=1;i<=n;i++) id[i]=i; sort(id+1,id+n+1,cmp); for (int i=1;i<=n;i++) dfn[id[i]]=i; tot=getans(); //solve(); cout<<tot; return 0; }
result：- rank-