poj 1556 The Doors 最短路 + 线段判交

田兵 — Tue, 21 Dec 2010 14:32:00 GMT

代码有点猥琐。纪念下第一道几何

Source Code

Problem: 1556  User: hehexiaobai
Memory: 1092K  Time: 0MS
Language: G++  Result: Accepted

Source Code
#include<iostream> // poj 1556
#include<cmath>
#include<cstring>
using namespace std;
const int MAX = 205;
const double epsilon = 1e-10;
const double PI = acos(-1.0);

double min(double a, double b){ return a > b ? b : a; }
double max(double a, double b){ return a > b ? a : b; }

struct Point
{
    double x, y;
    Point(){}
    Point(double a, double b): x(a), y(b){}

    Point operator + (Point b){
        return Point(x + b.x, y + b.y);
    }

    Point operator - (Point b){
        return Point(x - b.x, y - b.y);
    }

    double operator * (Point b){
        return x* b.y - y *b.x;
    }

    bool operator == (Point b){
        return (fabs(x - b.x)< epsilon) && (fabs(y - b.y) < epsilon);
    }
};

Point point[MAX];
double dis[MAX];
bool mp[MAX][MAX];
int nwalls, cntpoint;

int direction(Point &p0, Point & p1, Point & p2)//判断 p0p2是从向量p1p0绕p0的旋转方向
{
    double d = (p2 - p0) * (p1 - p0);
    if(fabs(d) < epsilon) return 0;  //共线

    if(d > 0.0) return 1;  //顺时针

    return -1;  //逆时针
}

bool inBox(Point &pi, Point & pj, Point &pk)
{
    return min(pi.x , pj.x) <= pk.x && pk.x <= max(pi.x, pj.x) &&
           min(pi.y , pj.y) <= pk.y && pk.y <= max(pi.y, pj.y);
}

bool segmentsIntersect(Point &p1, Point & p2, Point & p3, Point & p4)
{
    int d1 = direction(p3, p4, p1),
        d2 = direction(p3, p4, p2),
        d3 = direction(p1, p2, p3),
        d4 = direction(p1, p2, p4);

    if(d1 * d2 < 0  && d3 * d4 <0)
        return true;

    if( d1 == 0 && inBox(p3, p4, p1))
        return true;

    if( d2 == 0 && inBox(p3, p4, p2))
        return true;

    if( d3 == 0 && inBox(p1, p2, p3))
        return true;

    if( d4 ==0 && inBox(p1, p2, p4))
        return true;

    return false;
}

void Dijstra()
{
    int i,j ;
    double d[MAX][MAX] ;
    memset(d, 0, sizeof d);
    for( i = 0; i < cntpoint; i ++)
        for(j = i + 1; j < cntpoint; j++)
        {
            d[i][j] = d[j][i] = sqrt((point[i].x - point[j].x) * (point[i].x - point[j].x)
                                    + (point[i].y - point[j].y)*(point[i].y - point[j].y));
        }

    const double INF = 1e40;
    bool visit[MAX] = {0};

    for( i = 0; i < cntpoint; i ++)
        dis[i] = INF;
    dis[0] = 0.0;

    for( i = 0; i <cntpoint; i ++)
    {
        int index = -1;
        double min = INF;
        for(j = 0; j < cntpoint; j ++)
            if(!visit[j] && fabs(dis[j] - min) > epsilon && dis[j] < min)
            {
                index = j;
                min = dis[j];
            }

        if(index == -1)return;
        visit[index] = true;

        for( j = 0; j < cntpoint; j ++)
            if(!visit[j] && mp[index][j] == true && dis[j] > dis[index] + d[index][j])
                dis[j] = dis[index] + d[index][j];

    }
}

int main()
{

    int i , j;
    while(cin >> nwalls)
    {
        if( nwalls == -1)break;

        memset(point, 0, sizeof point);
        memset(mp, 0, sizeof (mp));
        memset(dis, 0, sizeof dis);

        point[0].x = 0.0;
        point[0].y = 5.0;

        double x, y1, y2, y3, y4;
        cntpoint = 1;
        for(i = 1;i <= nwalls; i ++)
        {
            cin >> x >> y1 >> y2 >> y3 >> y4;

            point[cntpoint].x = x;
            point[cntpoint].y = 0.0;
            cntpoint ++;

            point[cntpoint].x = x;
            point[cntpoint].y = y1;
            cntpoint ++;

            point[cntpoint].x = x;
            point[cntpoint].y = y2;
            cntpoint ++;

            point[cntpoint].x = x;
            point[cntpoint].y = y3;
            cntpoint ++;

            point[cntpoint].x = x;
            point[cntpoint].y = y4;
            cntpoint ++;

            point[cntpoint].x = x;
            point[cntpoint].y = 10.0;
            cntpoint ++;
        }

        point[cntpoint].x = 10.0;
        point[cntpoint].y = 5.0;
        cntpoint ++;

        int tempi, tempj;

        for( i = 0;  i < cntpoint ; i ++)
            for(j = i + 1; j < cntpoint; j ++)
            {
                tempi = i / 6;
                if( i % 6 != 0) tempi += 1;

                tempj = j/6;
                if( j % 6 != 0) tempj += 1;

                if(tempi == tempj)continue;
                if(point[i].y < epsilon || point[j].y < epsilon ||
                    10.0 - point[i].y < epsilon || 10.0 - point[j].y < epsilon)
                        continue;

                bool flag = true;
                for( int k = tempi + 1; k < tempj; k ++)
                {
                    int t = (k - 1) * 6;
                //    if(i == 0 && j == 9){ cout << flag << endl; cout << t << endl; }
                    if(segmentsIntersect(point[i],point[j],point[t + 1],point[t + 2]))flag = false;
                    if(segmentsIntersect(point[i],point[j],point[t + 3],point[t + 4]))flag = false;
                    if(segmentsIntersect(point[i],point[j],point[t + 5],point[t + 6]))flag = false;

                }
                if(flag == true)
                {
                    mp[i][j] = mp[j][i] = true;
                }
            }

    //    for( i = 0; i < cntpoint; i ++,cout << endl)
    //        for(j = 0; j < cntpoint; j ++)
    //            cout << mp[i][j] <<" ";



        Dijstra();
    //    for(i = 0; i < cntpoint ; i ++)
    //        cout << i <<' '<

        cout.precision(2);
        cout <<fixed << dis[cntpoint - 1] << endl;
    }

    return 0;
}
//0.0 0.0  1.0  1.0   1.0 0.0 1.0 1.0
//0.0 0.0  1.0  1.0   0.0 1.0 1.0  0.0
//0.0 0.0  1.0  1.0   1.0 0.0 1.0 0.9

田兵 2010-12-21 22:32 发表评论

C++博客-hehexiaobai-随笔分类-几何

poj 1556 The Doors 最短路 + 线段判交