Bumpy Objects UVA - 132

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这简直又是一道坑爹的题目，，，题意死活没看懂，，，，wa了我一天，，，

题意：object1 是6 是因为（1，6）构成的线段，（6，7）（7，1）这三条线段满足，取小是6

object2 （7，4）（4，6）（6，7）这三条线段满足所以为6，，，，

知道意思之后水题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <stdlib.h>
#include <string.h>

using namespace std;
const int maxn=111111;
const double eps=1e-8;

int sgn(double x)
{
    if(fabs(x)<eps)
        return 0;
    if(x<0)
        return -1;
    else
        return 1;
}

struct Point
{
    double x,y;
    int index;
    Point(){}
    Point(double _x,double _y)
    {
        x=_x;
        y=_y;
    }
    Point operator -(const Point &b)const
    {
        return Point(x-b.x,y-b.y);
    }
    double operator ^(const Point &b)const
    {
        return x*b.y-y*b.x;
    }
    double operator *(const Point &b)const
    {
        return x*b.x+y*b.y;
    }
};

struct Line
{
    Point s,e;
    Line(){};
    Line(Point _s,Point _e)
    {
        s=_s;
        e=_e;
    }
};

Point p[maxn];
Point p1[maxn];
Point p3[maxn];
int check[maxn];
int cont;
double dist(Point a,Point b)
{
    return sqrt((a-b)*(a-b));
}

bool cmp(Point a,Point b)
{
    int ans=sgn((a-p[0])^(b-p[0]));
    if(ans==1)
        return true;
    else if(ans==0)
        return dist(a,p[0])<dist(b,p[0]);
    else
        return false;
}

int Stack[maxn];
int top;
void graham()
{
    for(int i=0;i<cont;i++)
    {
        if(p[i].y<p[0].y||(p[i].y==p[0].y&&p[i].x<p[0].x))
            swap(p[i],p[0]);
    }
    sort(p+1,p+cont,cmp);
    Stack[0]=0;
    Stack[1]=1;
    top=2;
    for(int i=2;i<cont;i++)
    {
        while(top>1&&((p[Stack[top-1]]-p[Stack[top-2]])^(p[i]-p[Stack[top-2]]))<=0)
            top--;
        Stack[top++]=i;
    }
}

vector <Point> ve;
int main()
{
    char str[100];
    while(1)
    {
        gets(str);
        if(strlen(str)==1&&str[0]=='#')
            break;
        Point p2;
        double x,y;
        ve.clear();
        scanf("%lf %lf",&x,&y);
        p2=Point(x,y);
        cont=0;
        while(1)
        {
            double x1,y1;
            scanf("%lf %lf",&x1,&y1);
            if(x1==0&&y1==0)
                break;
            p[cont]=Point(x1,y1);
            p[cont].index=cont+1;
            ve.push_back(p[cont]);
            cont++;
        }
        for(int i=1;i<ve.size();i++)
        {
            if(sgn((ve[i-1]-ve[i])^(ve[(i+1)%ve.size()]-ve[i]))==0)
                ve.erase(ve.begin()+i);
        }
        /*for(int i=0;i<ve.size();i++)
        {
            cout<<ve[i].x<<" "<<ve[i].y<<ve[i].index<<endl;
        }*/
            graham();
            for(int i=0;i<top;i++)
            {
                p1[i]=p[Stack[i]];
                p1[i].index=p[Stack[i]].index;
                //cout<<p1[i].x<<" "<<p1[i].y<<" "<<p1[i].index<<endl;
            }
            int max1=1000000000;
            for(int i=0;i<top;i++)
            {
                if(sgn((p1[i]-p2)^(p1[(i+1)%top]-p2))==1&&sgn((p2-p1[i])*(p1[(i+1)%top]-p1[i]))==1&&sgn((p2-p1[(i+1)%top])*(p1[i]-p1[(i+1)%top]))==1)
                {

                        max1=min(max1,max(p1[i].index,p1[(i+1)%top].index));

                }
            }
        printf("%s %d\n",str,max1);
        getchar();
    }
    return 0;
}