3712: [PA2014]Fiolki

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstring>
using namespace std;

#define M 500010
#define L 20

int x,y,mcd;
int n,m,k,t,num,tot;
int g[M],f[M],fa[M][23],dep[M],dfn[M],head[M];
long long ans;

struct edge{int to,nex;}e[M*4];
struct node{int x,y,deep,id;}tmp[M];

bool operator <(node a,node b){return a.deep==b.deep&&a.id<b.id||(a.deep>b.deep);}//坑啊

void add(int u,int v){e[t]=(edge){v,head[u]};head[u]=t++;}
void insert(int u,int v){add(u,v);add(v,u);}

void dfs(int x,int tim){
dfn[x]=tim;
for(int i=1;i<=L;i++) fa[x][i]=fa[fa[x][i-1]][i-1];
for(int i=head[x];i!=-1;i=e[i].nex){
int v=e[i].to;
if(v!=fa[x][0]){
fa[v][0]=x,dep[v]=dep[x]+1;
dfs(v,tim);
}
}
}

int lca(int x,int y){
if(dep[x]<dep[y]) swap(x,y);
for(int i=0;i<=L;i++) if((dep[x]-dep[y])&(1<<i)) x=fa[x][i];
if(x==y) return x;
for(int i=L;i>=0;i--)
if(fa[x][i]!=fa[y][i]) x=fa[x][i],y=fa[y][i];
retu
b0ef
rn fa[x][0];
}

void work()
{
for(int i=1;i<=tot;i++){
x=tmp[i].x,y=tmp[i].y,mcd=min(g[x],g[y]);
g[x]-=mcd,g[y]-=mcd,ans+=mcd;
}
cout<<ans*2<<endl;
}

void init()
{
t=0;memset(head,-1,sizeof(head));
cin>>n>>m>>k;
for(int i=1;i<=n;i++) scanf("%d",&g[i]);
for(int i=1;i<=n;i++) f[i]=i;
for(int i=1;i<=m;i++)
scanf("%d%d",&x,&y),insert(n+i,f[x]),insert(n+i,f[y]),f[y]=n+i;
for(int i=n+m;i>=1;i--) if(!fa[i][0]) dfs(i,++num);
for(int i=1;i<=k;i++){
scanf("%d%d",&x,&y);
if(dfn[x]==dfn[y]) tmp[++tot]=(node){x,y,dep[lca(x,y)],i};
}
sort(tmp+1,tmp+tot+1);
}

int main()
{
init();
work();
return 0;
}