70 lines
1.5 KiB
C++
70 lines
1.5 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<iostream>
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#include<vector>
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#include<string>
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#include<set>
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#include<algorithm>
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#include<map>
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#include<iostream>
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using namespace std;
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const int inf = 100000;
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const int maxn = 101;
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vector<int> edge[maxn];
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int a[maxn],b[maxn];
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int f[maxn][2],g[maxn][2];
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void dfs(int u,int fa)
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{
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f[u][0]=0;
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g[u][0]=0;
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int sz=edge[u].size();
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int m1=inf,m2=inf;
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bool leaf=true;
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for(int i=0;i<sz;i++)
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{
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int v=edge[u][i];
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if(v==fa) continue;
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dfs(v,u);
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leaf=false;
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int tmp=min(f[v][0],g[v][1]);
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f[u][0]+=tmp;
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m1=min(m1,f[v][1]-tmp);
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tmp=min(g[v][0],f[v][1]);
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g[u][0]+=tmp;
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m2=min(m2,g[v][1]-tmp);
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}
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if(leaf)
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{
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f[u][1]=a[u];
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f[u][0]=a[u]/2;
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g[u][1]=b[u];
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g[u][0]=b[u]/2;
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}
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else
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{
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f[u][1]=f[u][0] + min(a[u],m1+a[u]/2);
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f[u][0]+=a[u]/2;
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g[u][1]=g[u][0] + min(b[u],m2+b[u]/2);
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g[u][0]+=b[u]/2;
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}
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}
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int main()
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{
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int n;
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while(scanf("%d",&n)!=EOF)
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{
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for(int i=0;i<=n;i++) edge[i].clear();
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for(int i=1;i<=n;i++) scanf("%d",&a[i]);
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for(int i=1;i<=n;i++) scanf("%d",&b[i]);
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for(int i=1,u,v;i<n;i++)
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{
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scanf("%d%d",&u,&v);
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edge[u].push_back(v);
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edge[v].push_back(u);
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}
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dfs(1,0);
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printf("%d\n",min(f[1][1],g[1][1]));
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}
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return 0;
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}
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