hdu 1542 线段树+扫描线+离散化~~

第一道额~~理解了好久~

思路基本都是网上的~

#include <iostream>#include <cstring>#include <cstdio>#include <algorithm>#include <map>#define lson pos<<1#define rson pos<<1|1using namespace std;const int MAXN=1000005;struct line{    double l,r,h;    int f;    line(double a=0,double b=0,double c=0,int d=0):    l(a),r(b),h(c),f(d){}};line a[MAXN];double x[MAXN];bool cmp(const line &lhs,const line &rhs){    return lhs.h<rhs.h;}struct node{    int l,r;    double sum;    int cover;    int mid()    {        return (l+r)>>1;    }};node tree[MAXN*4];void pushup(int pos);void build(int l,int r,int pos){    tree[pos].l=l;    tree[pos].r=r;    if(l==r)    {        tree[pos].sum=0;        tree[pos].cover=0;        return ;    }    int mid=tree[pos].mid();    build(l,mid,lson);    build(mid+1,r,rson);    tree[pos].cover=0;    tree[pos].sum=0;}void pushup(int pos){    if(tree[pos].cover)    {        int l=tree[pos].l;        int r=tree[pos].r+1;        tree[pos].sum=x[r]-x[l];    }    else if(tree[pos].l==tree[pos].r)        tree[pos].sum=0;    else        tree[pos].sum=tree[lson].sum+tree[rson].sum;}void update(int l,int r,int f,int pos){    if(l==tree[pos].l&&r==tree[pos].r)    {        tree[pos].cover+=f;        pushup(pos);        return ;    }    int mid=tree[pos].mid();    if(r<=mid)        update(l,r,f,lson);    else if(l>mid)        update(l,r,f,rson);    else    {        update(l,mid,f,lson);        update(mid+1,r,f,rson);    }    pushup(pos);}int main(){    int n;    int cas=0;    while(scanf("%d",&n),n)    {        int i;        cas++;        map<double,int> mp;        int k=0;        int k1=1;        for(i=0;i<n;i++)        {            double x1,y1,x2,y2;            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);            a[k++]=line(x1,x2,y1,1);            a[k++]=line(x1,x2,y2,-1);            if(mp[x1]==0)            {                mp[x1]=k1;                x[k1]=x1;                k1++;            }            if(mp[x2]==0)            {                mp[x2]=k1;                x[k1]=x2;                k1++;            }        }        build(1,k1-1,1);        sort(a,a+k,cmp);        sort(x+1,x+k1);        for(i=1;i<k1;i++)            mp[x[i]]=i;        double ans=0;        for(i=0;i<k-1;i++)        {            int l=mp[a[i].l];            int r=mp[a[i].r]-1;            update(l,r,a[i].f,1);            ans+=(a[i+1].h-a[i].h)*tree[1].sum;        }        printf("Test case #%d\n",cas);        printf("Total explored area: %.2lf\n\n",ans);    }    return 0;}