B. Alyona and a tree

二分+dfs序+前缀和+瞎几把yy

#include "a.h"

int n;
aLL a;
struct edge
{
  int to, nx, w;
} e[N << ];
arr fi;
int ce = ;
aLL sum, ans;
aLL vec, up, down, res;
ll tot = ;
ll rs = ;

inline void add(int u, int v, int w)
{
  e[++ce] = edge{v, fi[u], w};
  fi[u] = ce;
}

void dfs(int x)
{
  if (fi[x] == -)
  {
    rs = res[x];
    rs += up[x], rs -= down[x];
    ans[x] = rs;
    return;
  }
  for (int i = fi[x]; i != -; i = e[i].nx)
  {
    int v = e[i].to, w = e[i].w;
    sum[++tot] = sum[tot - ] + w;
    int p = lower_bound(sum + , sum +  + tot, sum[tot] - a[v]) - sum;
    if (tot -  >= p)
      up[vec[tot - ]]++, down[vec[p - ]]++;
    vec[tot] = v;
    dfs(v);
    tot--;
    res[x] += rs;
    rs = ;
  }
  rs = res[x];
  rs += up[x], rs -= down[x];
  ans[x] = rs;
}

int main()
{
  // file("test");
  while (~scanf("%d", &n))
  {
    me(fi, -);
    For(i, , n) sdf(a[i]);
    For(i, , n)
    {
      int x, y;
      sdf(x), sdf(y);
      add(x, i, y);
    }
    vec[] = ;
    sum[] = ;
    dfs();
    For(i, , n)
        printf("%d ", ans[i]);
  }
  return ;
}