hdu1828 线段树+离散化+扫描线

添加lb[],rb[]数组，来标记竖边。添加num，来计算竖边的个数，因为计算周长的时候，未覆盖的竖边都要加。

#include<stdio.h>
#include<stdlib.h>
#include<algorithm>
using namespace std;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define maxn 10010
struct seg
{
    int l,r,h;
    int f;
}s[maxn<<];
struct node
{
    int cnt;
    int num;
    int len;
}tree[maxn<<];
int lb[maxn<<],rb[maxn<<];
int mark[maxn];
bool cmp(seg a,seg b)
{
    return a.h < b.h;
}
void build(int l,int r,int rt)
{
    tree[rt].cnt=;
    tree[rt].len=;
    tree[rt].num=;
    if(l==r)
        return ;
    int m=(l+r)/;
    build(lson);
    build(rson);
}
void getlen(int l,int r,int rt)
{
    if(tree[rt].cnt)//如果这一段被全部覆盖
    {
        tree[rt].len=mark[r+]-mark[l];
        tree[rt].num=;//整段覆盖，那就有2条竖直的边
        lb[rt]=rb[rt]=;//标记左右的竖直线段
    }
    else if(l==r)
    {
        tree[rt].num=tree[rt].len=;
        lb[rt]=rb[rt]=;
    }
    else //未整段覆盖;
    {
        tree[rt].num=tree[rt<<].num+tree[rt<<|].num;
        tree[rt].len=tree[rt<<].len+tree[rt<<|].len;
        lb[rt]=lb[rt<<];rb[rt]=rb[rt<<|];
        if(lb[rt<<|]&&rb[rt<<])//此线段已相连
            tree[rt].num-=;
    }
}
void updata(int L,int R,int c,int l,int r,int rt)
{
    if(l>=L&&R>=r)
    {
        tree[rt].cnt+=c;
        getlen(l,r,rt);
        return ;
    }
    int m=(l+r)/;
    if(m>=L)
        updata(L,R,c,lson);
    if(R>m)
        updata(L,R,c,rson);
    getlen(l,r,rt);
}
int find(int val,int len)
{
    int l,r,m;
    l=;
    r=len;
    while(l<=r)
    {
        m=(l+r)/;
        if(val==mark[m])
            return m;
        else if(val>mark[m])
            l=m+;
        else r=m-;
    }
    return -;
}
int main()
{
    int i,n,m;
    while(scanf("%d",&n)!=EOF)
    {
        int x1,y1,x2,y2;
        m = ;
        for(i=;i<n;i++)
        {
            scanf("%d %d %d %d",&x1,&y1,&x2,&y2);
            s[m].l = x1; s[m].r = x2; s[m].h = y1; s[m].f = ; mark[m++] = x1;
            s[m].l = x1; s[m].r = x2; s[m].h = y2; s[m].f = -; mark[m++] = x2;
        }
        sort(mark,mark+m);
        sort(s,s+m,cmp);
        int k = ;
        for(i=;i < m;i++)
        {
            if(mark[i]!=mark[i-])
                mark[k++]=mark[i];
        }
        build(,k-,);
        int ans=;
        int past=;
        for(i=;i<m;i++)
        {
            int l=find(s[i].l,k-);
            int r=find(s[i].r,k-)-;
            updata(l,r,s[i].f,,k-,);
            ans+=(tree[].num*(s[i+].h-s[i].h));
            ans+=abs(tree[].len-past);
            past=tree[].len;
        }
        printf("%d\n",ans);
    }
}