POJ2528(离散化+线段树区间更新)

#include"cstdio"
#include"algorithm"
using namespace std;
const int MAXN=10005;
struct Post{
    int l,r;
}posters[MAXN];
int x[MAXN*2];
int hash[10000005];
struct node{
    int l,r;
    bool beCovered;
};
int cnt;
node a[MAXN*8];//*4 会RE ?? 

void build(int rt,int l,int r)
{
    a[rt].l=l;
    a[rt].r=r;
    if(l==r)
    {
        a[rt].beCovered=false;
        return ;
    }
    
    int mid=(l+r)>>1;
    build(rt<<1,l,mid);
    build((rt<<1)|1,mid+1,r);
    a[rt].beCovered=(a[rt<<1].beCovered&&a[(rt<<1)|1].beCovered);
}

void update(int rt,int l,int r)
{
    if(a[rt].l==l&&a[rt].r==r)
    {
        a[rt].beCovered=true;
        return ;
    }
    
    if(a[rt].beCovered)
    {
        a[rt<<1].beCovered=true;
        a[(rt<<1)|1].beCovered=true;
    }
    
    int mid=(a[rt].l+a[rt].r)>>1;
    if(r<=mid)    update(rt<<1,l,r);
    else if(mid<l)    update((rt<<1)|1,l,r);
    else
    {
        update(rt<<1,l,mid);
        update((rt<<1)|1,mid+1,r);
    }
    a[rt].beCovered=(a[rt<<1].beCovered&&a[(rt<<1)|1].beCovered);
}

bool query(int rt,int l,int r)
{
    if(a[rt].l==l&&a[rt].r==r)
    {
        return a[rt].beCovered;
    }
    
    if(a[rt].beCovered)
    {
        a[rt<<1].beCovered=true;
        a[(rt<<1)|1].beCovered=true;
    }
    
    int mid=(a[rt].l+a[rt].r)>>1;
    if(r<=mid)    return query(rt<<1,l,r);
    else if(mid<l)    return query((rt<<1)|1,l,r);
    else{
        return (query(rt<<1,l,mid)&&query((rt<<1)|1,mid+1,r));
    }
    
}

int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        cnt=0;
        int n;
        scanf("%d",&n);        
        for(int i=0;i<n;i++)
        {
            scanf("%d%d",&posters[i].l,&posters[i].r);
            x[cnt++]=posters[i].l;
            x[cnt++]=posters[i].r;
        }
        sort(x,x+cnt);
        cnt=unique(x,x+cnt)-x;
        for(int i=0;i<cnt;i++)
        {
            hash[x[i]]=i+1;
        }
        //区间离散化完毕 
        build(1,1,cnt);
        int res=0;
        for(int i=n-1;i>=0;i--)
        {
            if(!query(1,hash[posters[i].l],hash[posters[i].r]))    res++;
            update(1,hash[posters[i].l],hash[posters[i].r]);
        }
        printf("%d\n",res);
    }
                
    return 0;
}