JZOJ6285飘雪圣域

Posted 2020-12-01 horizonwd

description

---

analysis

• 从求联通块出发根本没做法，于是考虑连通块里面的边

• 对于一个询问([l,r])，一条边的左端点(≥l)且右端点(≤r)才在这个区间的点之间

• 于是对于边和询问排序，依次把边加入树状数组，然后查询当前询问区间里的边条数就知道了联通块个数

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code

#pragma GCC optimize("O3")
#pragma G++ optimize("O3")
#include<stdio.h>
#include<string.h>
#include<algorithm>
#define MAXN 200005
#define ll long long
#define reg register ll
#define fo(i,a,b) for (reg i=a;i<=b;++i)
#define fd(i,a,b) for (reg i=a;i>=b;--i)

using namespace std;

ll tr[MAXN];
ll n,q;

struct edge
{
    ll x,y;
}a[MAXN];

struct inquiry
{
    ll x,y,z,ans;
}b[MAXN];

inline ll read()
{
    ll x=0,f=1;char ch=getchar();
    while (ch<'0' || '9'<ch){if (ch=='-')f=-1;ch=getchar();}
    while ('0'<=ch && ch<='9')x=x*10+ch-'0',ch=getchar();
    return x*f;
}
inline ll lowbit(ll x){return x&(-x);}
inline bool cmp(edge a,edge b){return a.y<b.y;}
inline bool cmpp(inquiry a,inquiry b){return a.y<b.y;}
inline bool cmppp(inquiry a,inquiry b){return a.z<b.z;}
inline void modify(ll x,ll y){while (x<=n)tr[x]+=y,x+=lowbit(x);}
inline ll query(ll x){ll y=0;while (x)y+=tr[x],x-=lowbit(x);return y;} 
inline ll get(ll x,ll y){return query(y)-query(x-1);}
int main()
{
    freopen("icekingdom.in","r",stdin);
    //freopen("icekingdom.out","w",stdout);
    n=read(),q=read();
    fo(i,1,n-1)
    {
        ll x=read(),y=read();
        a[i].x=min(x,y),a[i].y=max(x,y);
    }
    sort(a+1,a+n,cmp);
    fo(i,1,q)b[i].x=read(),b[i].y=read(),b[i].z=i;
    sort(b+1,b+q+1,cmpp);ll j=1;
    fo(i,1,q)
    {
        while (j<n && b[i].y>=a[j].y)modify(a[j++].x,1);
        b[i].ans=b[i].y-b[i].x+1-get(b[i].x,b[i].y);
    }
    sort(b+1,b+q+1,cmppp);
    fo(i,1,q)printf("%lld
",b[i].ans);
    return 0;
}