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5 1 1 1 1 1 1 2 2 3 3 4 4 5
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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define prt(k) cout<<#k" = "<<k<<endl;
const int inf = 0x3f3f3f3f;
const int N = 100007;
const int W = 107;
int f[N][107], g[N][107];
int father[N];
int n;
int w[N];
int F[N][107], G[N][107];
int maxw;
struct edge
{
int v, next;
}e[N<<1];
int head[N], mm;
void add(int u, int v)
{
e[mm].v = v;
e[mm].next = head[u];
head[u] = mm++;
}
struct P
{
int d, id;
P() {}
P(int _id, int _d=0) { d=_d, id=_id; }
bool operator < (P b) const
{
return d > b.d;
}
}p[N];
bool vis[N];
void bfs()
{
queue<P> q;
q.push(P(1,0));
memset(vis,0,sizeof vis);
vis[1] = true;
father[1] = 1;
while (!q.empty()) {
P u = q.front(); q.pop();
int now = u.id;
p[now].id = now;
p[now].d = u.d + 1;
for (int i=head[now];~i;i=e[i].next) {
int v = e[i].v;
if (!vis[v]) {
q.push(P(v, u.d + 1));
vis[v] = true;
father[v] = now;
}
}
}
}
void gao(int u, int fa)
{
assert(!vis[u]);
vis[u] = true;
bool flag = false;
for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
flag = true;
assert(vis[v]);
}
if (!flag) {
g[u][0] = 0;
f[u][w[u]] = 1;
}
for (int j=0;j<=maxw;j++) {
ll sum=0;
for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
int t = F[v][j+1];
if (j > 0)
t = min(t, G[v][j-1]);
sum += t;
if (sum >= inf) { sum = inf; break; }
}
if (sum < inf ) for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
int t = F[v][j+1];
if (j > 0) t = min(t, G[v][j-1]);
if (0<=sum && sum < inf) f[u][j] = min(f[u][j], (int)(f[v][j+1] + sum - t ) ) ;
}
sum = 0;
int t;
for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
int t = F[v][j];
if (j > 0) t = min(t, G[v][j-1]);
sum += t;
if (sum >= inf) { sum = inf; break; }
}
if (j>0 && sum < inf) for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
int t = F[v][j];
if (j > 0) t = min(t, G[v][j-1]);
if (0<=sum && sum < inf) g[u][j]=min(g[u][j], (int)(g[v][j-1] + sum - t ) );
}
}
ll sum = 0;
for (int i=head[u];~i;i=e[i].next) {
int v = e[i].v;
if (v==fa) continue;
sum += min(F[v][w[u]+1], w[u]>0 ? G[v][w[u]-1] : inf);
}
if (0<=sum && sum<inf) f[u][w[u]]=min(f[u][w[u]], int(1 + sum ));
F[u][0] = f[u][0];
G[u][0] = g[u][0];
for (int j=1;j<=maxw+1;j++) {
F[u][j] = min(F[u][j-1], f[u][j]);
G[u][j] = min(G[u][j-1], g[u][j]);
}
}
int main()
{
while (scanf("%d", &n)==1) {
maxw = 0;
for (int i=1;i<=n;i++) scanf("%d", w+i), maxw=max(maxw, w[i]);
mm=0; memset(head,-1,sizeof head);
for (int i=1;i<=n-1;i++)
{
int u, v; scanf("%d%d", &u, &v);
add(u, v);
add(v, u);
}
memset(f, 63, sizeof f);
memset(g, 63, sizeof g);
bfs();
sort(p+1, p+n+1);
memset(vis, 0, sizeof vis);
for (int i=1;i<=n;i++) {
gao(p[i].id, father[p[i].id]);
}
int ans = n;
for (int i=0;i<=maxw;i++)
ans = min(ans, f[1][i]);
printf("%d\n", ans);
}
}
/**
3
1 1 1
1 2
2 3
7
1 1 1 1 1 1 1
1 2
2 3
3 4
4 5
5 6
6 7
4
0 1 0 1
1 2
1 3
1 4
4
0 2 0 0
1 2
1 3
1 4
*/
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原文地址：http://blog.csdn.net/oilover/article/details/47087655
