扫描线 模板

测试题目：HDU 1542

using namespace std;const int maxn = 100 + 5;const int TOT_SEG = maxn * 2;/** Seg**  l,r,h 分别为线段的左端点，右端点，高**  f 标识上下边*/struct Seg{    int f;    double l,r,h;    void set(double ll,double rr,double hh,int d){        l = ll,r = rr,h = hh,f = d;    }}Segs[TOT_SEG];bool cmp(const Seg& a,const Seg& b){    return a.h < b.h;}double AR[TOT_SEG]; /** 区间长度 */map<double,int> POS; /** 将端点 HASH 到区间上 */int Seg_CNT,HASH_SEG_CNT;void SEG_HASH(){    POS.clear();HASH_SEG_CNT = 2;    sort(Segs + 1,Segs + Seg_CNT,cmp);    sort(AR + 1,AR + Seg_CNT);    for(int i = 2;i < Seg_CNT;++i){        if(AR[i] != AR[i - 1]){            AR[HASH_SEG_CNT] = AR[i];            POS[AR[i]] = HASH_SEG_CNT++;        }    }    for(int i = 1;i < HASH_SEG_CNT;++i){        AR[i] = AR[i + 1] - AR[i];    }}

HDU 1542 代码：

#include <bits/stdc++.h>#define sf scanf#define pf printfusing namespace std;const int maxn = 100 + 5;const int TOT_SEG = maxn * 2;/** Seg**  l,r,h 分别为线段的左端点，右端点，高**  f 标识上下边*/struct Seg{    int f;    double l,r,h;    void set(double ll,double rr,double hh,int d){        l = ll,r = rr,h = hh,f = d;    }}Segs[TOT_SEG];bool cmp(const Seg& a,const Seg& b){    return a.h < b.h;}double AR[TOT_SEG]; /** 区间长度 */map<double,int> POS; /** 将端点 HASH 到区间上 */int Seg_CNT,HASH_SEG_CNT;void SEG_HASH(){    POS.clear();HASH_SEG_CNT = 2;    sort(Segs + 1,Segs + Seg_CNT,cmp);    sort(AR + 1,AR + Seg_CNT);    for(int i = 2;i < Seg_CNT;++i){        if(AR[i] != AR[i - 1]){            AR[HASH_SEG_CNT] = AR[i];            POS[AR[i]] = HASH_SEG_CNT++;        }    }    for(int i = 1;i < HASH_SEG_CNT;++i){        AR[i] = AR[i + 1] - AR[i];    }}int FALG[TOT_SEG];/** SEG_TREE */#define lson rt << 1 , l , mid#define rson rt << 1 | 1,mid + 1,rdouble _SUM[TOT_SEG << 2];void PushUp(int rt){    _SUM[rt] = _SUM[rt << 1] + _SUM[rt << 1 | 1];}void Build(int rt,int l,int r){    if(l == r){        _SUM[rt] = FALG[l] = 0;        return;    }    int mid = l + r >> 1;    Build(lson),Build(rson);}void Update(int rt,int l,int r,int L,int R,int d){    if(l == r){        FALG[l] += d;        if(FALG[l] == 0) _SUM[rt] = 0;        else _SUM[rt] = AR[r];        return;    }    int mid = l + r >> 1;    if(L <= mid) Update(lson,L,R,d);    if(R > mid) Update(rson,L,R,d);    PushUp(rt);}int main(){    int n,ca = 0;    while( ~sf("%d",&n) && n ){        int tmp = 1;double x1,x2,y1,y2;        for(int i = 0;i < n;++i){            sf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);            Segs[tmp].set(x1,x2,y1,1);            AR[tmp++] = x1;            Segs[tmp].set(x1,x2,y2,-1);            AR[tmp++] = x2;        }//        POS.clear();//        sort(Segs + 1,Segs + tmp,cmp);//        sort(AR + 1,AR + tmp);//        AR[tmp] = -1;//////        /** 点去重 + 点HASH*///        int AR_TMP = 2;//        for(int i = 2;i < tmp;++i)//            if(AR[i] != AR[i - 1]){//                AR[AR_TMP] = AR[i];//                POS[AR[i]] = AR_TMP++;//            }////        /** 点变为区间 *///        for(int i = 1;i < AR_TMP;++i){//            AR[i] = AR[i + 1] - AR[i];//        }        Seg_CNT = tmp;        SEG_HASH();        int AR_TMP = HASH_SEG_CNT;        Build(1,1,AR_TMP - 2);        double ans = 0;        for(int i = 1;i < tmp;++i){            int L = POS[Segs[i].l],R = POS[Segs[i].r] - 1;            Update(1,1,AR_TMP - 2,L,R,Segs[i].f);            ans = ans + _SUM[1] * (Segs[i + 1].h - Segs[i].h);        }        pf("Test case #%d\n",++ca);        pf("Total explored area: %.2lf\n\n",ans);    }}