bzoj3252

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, int> PII;
const int N = 200010;
struct edge {
    int nxt, to;
} e[N << 1];
int n, k, cnt = 1, tot;
ll ans;
int head[N], dfn[N], low[N], fa[N], mp[N];
ll v[N], w[N], tag[N << 2];
PII tree[N << 2];
void link(int u, int v)
{
    e[++cnt].nxt = head[u];
    head[u] = cnt;
    e[cnt].to = v;
}
namespace seg
{
    void pushdown(int x)
    {
        if(!tag[x]) return;
        tree[x << 1].first += tag[x]; tree[x << 1 | 1].first += tag[x];
        tag[x << 1] += tag[x]; tag[x << 1 | 1] += tag[x];
        tag[x] = 0;         
    }
    void build(int l, int r, int x)
    {
        if(l == r) { tree[x].first = w[mp[l]]; tree[x].second = mp[l]; return; }
        int mid = (l + r) >> 1;
        build(l, mid, x << 1); build(mid + 1, r, x << 1 | 1);
        if(tree[x << 1].first > tree[x << 1 | 1].first) tree[x] = tree[x << 1];
        else tree[x] = tree[x << 1 | 1];
    }
    void update(int l, int r, int x, int a, int b, int num)
    {
        if(l > b || r < a) return;
        if(l >= a && r <= b)
        {
            tree[x].first += num; tag[x] += num; return; 
        }
        pushdown(x);
        int mid = (l + r) >> 1;
        update(l, mid, x << 1, a, b, num);
        update(mid + 1, r, x << 1 | 1, a, b, num);
        if(tree[x << 1].first > tree[x << 1 | 1].first) tree[x] = tree[x << 1];
        else tree[x] = tree[x << 1 | 1]; 
    }
} using namespace seg;
void dfs(int u, int last, ll sum)
{
    dfn[u] = ++tot; mp[tot] = u; w[u] = sum;
    for(int i = head[u]; i; i = e[i].nxt) if(e[i].to != last)
    {
        fa[e[i].to] = u;
        dfs(e[i].to, u, sum + v[e[i].to]);
    }
    low[u] = tot;
}
void change(int pos)
{
    while(v[pos])
    {
        update(1, n, 1, dfn[pos], low[pos], -v[pos]);
        v[pos] = 0; pos = fa[pos];
    }
}
int main()
{
    scanf("%d%d", &n, &k);
    for(int i = 1; i <= n; ++i) scanf("%lld", &v[i]);
    for(int i = 1; i < n; ++i)
    {
        int u, v; scanf("%d%d", &u, &v);
        link(u, v); link(v, u);
    }
    ans = v[1];
    v[1] = 0;
    dfs(1, 0, 0);
    build(1, n, 1);
    while(k--)
    {
        PII x = tree[1];
        ans += x.first;
        change(x.second);    
    }
    printf("%lld\n", ans);
    return 0;
}