求助，抱零了

样例都过了，对着题解改瞎了

#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(register int i=a;i<=b;++i)
#define Rep(i,a,b) for(register int i=a;i>=b;--i)
inline int read()
{
    bool f=0;int x=0;char ch;
    do{ch=getchar();f|=(ch=='-');}while(!isdigit(ch));
    do{x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}while(isdigit(ch));
    return f?-x:x;
}
inline void write(int x)
{
    if(x<0)x=-x,putchar('-');
    if(x>9)write(x/10);putchar(x%10+'0');
}
inline void writesp(int x)
{
    write(x);putchar(' ');
}
inline void writeln(int x)
{
    write(x);puts("");
}
const int maxn=6e5+5;
int head[maxn],to[maxn<<1|1],nxt[maxn<<1|1],tot=0;
void addedge(int u,int v)
{
    nxt[++tot]=head[u];
    head[u]=tot;
    to[tot]=v;
}
int dfn[maxn],dep[maxn],siz[maxn],cnt=0;
void dfs(int u,int fa)
{
    dfn[u]=++cnt;
    siz[u]=1;
    dep[u]=dep[fa]+1;
    for(register int i=head[u];i;i=nxt[i])
    {
        int v=to[i];
        if(v==fa)continue;
        dfs(v,u);
        siz[v]=siz[u]+1;
    }
}
int tree[maxn];
inline int lowbit(int x){return x&(-x);}
void add(int x,int k)
{
    for(;x<=maxn;x+=lowbit(x))
    {
        tree[x]+=k;
    }
}
int sum(int x)
{
    int res=0;
    for(;x;x-=lowbit(x))
    {
        res+=tree[x];
    }
    return res;
}
struct point
{
    int dep;
    int dfn;
    int val;
    bool operator <(const point &b)const
    {
        return dep<b.dep;
    }
}a[maxn];
int res[maxn]; 
struct query
{
    int x,y,z,id;
    bool operator <(const query &b)const 
    {
        return z<b.z;
    }
}q[maxn<<1|1];
int main()
{
    int n=read(),m=read();
    rep(i,1,n-1)
    {
        int u=read(),v=read();
        addedge(u,v);addedge(v,u);
    }
    dfs(1,0);
    rep(i,1,n)
    {
//      --dep[i];
        a[i]=(point){dep[i],dfn[i],siz[i]-1};
    }
    rep(i,1,m)
    {
        int p=read(),k=read();
        res[i]+=min(dep[p],k)*(siz[p]-1);
        q[(i<<1)-1]=(query){dfn[p],dfn[p]+siz[p]-1,dep[p],-i};
        q[i<<1]=(query){dfn[p],dfn[p]+siz[p]-1,dep[p]+k,i};
    }
    sort(a+1,a+1+n);sort(q+1,q+1+(m<<1));
    for(register int i=1,j=1;i<=(m<<1);++i)
    {
        while(j<=n&&a[j].dep<q[i].z)add(a[j].dfn,a[j].val),++j;
        register int cur=abs(q[i].id);
        if(q[i].id<0)res[q[i].id]-=sum(q[i].y)-sum(q[i].x);
        else res[q[i].id]+=sum(q[i].y)-sum(q[i].x);
    }
    rep(i,1,m)
    {
        writeln(res[i]);
    }
    return 0;
}