LCP 37. 最小矩形面积

我们发现对于对答案有影响的点只能有斜率相邻的线能够产生，因此我们可以把斜率相同的放在一组，相邻计算即可。

class Solution {
public:
    static bool cmp(pair<int,int> x,const pair<int,int> y){
        if(x.first!=y.first)return x.first<y.first;
        else return x.second<y.second;
    }
    double minRecSize(vector<vector<int>>& lines) {
        map<int,pair<int,int> > sq;//up down max
        pair<int,int> st[123456];
        int len=(int)lines.size();
        for(int i=0;i<(int)lines.size();i++){
            st[i]=make_pair(lines[i][0],lines[i][1]);
        }
        //cout<<st[0].first<<" "<<st[0].second<<endl;
        sort(st,st+len,cmp);
        double l,u,r,d;
        l=u=r=d=0;
        int count=0;
        sq[st[0].first]=make_pair(st[0].second,st[0].second);
        int last=st[0].first;
        //cout<<sq[last].first<<" "<<sq[last].second<<endl;
        for(int i=1;i<len;i++){
            //cout<<l<<" "<<r<<" "<<u<<" "<<d<<endl;
            if(st[i].first==st[i-1].first){
                int q=st[i].first;
                int s=st[i].second;
                if(sq[q].first<s)sq[q].first=s;
                if(sq[q].second>s)sq[q].second=s;
                //crazy
                if(q==last)continue;
                int dd1=st[i].second-sq[last].first;
            int dd2=st[i].second-sq[last].second;
            int qq=st[i].first-last;
            double x1= -1.0*dd1/qq;
            double x2=-1.0*dd2/qq;
            double y1= st[i].first*x1+st[i].second;
            double y2=st[i].first*x2+st[i].second;
            if(count==0){
                l=r=x1;
                u=d=y1;
            }
                if(x1>r)r=x1;
                if(x1<l)l=x1;
                if(y1>u)u=y1;
                if(y1<d)d=y1;
                if(x2>r)r=x2;
                if(x2<l)l=x2;
                if(y2>u)u=y2;
                if(y2<d)d=y2;
        
            count++;
                continue;
            }
            last=st[i-1].first;
            //bug 
            sq[st[i].first]=make_pair(st[i].second,st[i].second);
            int dd1=st[i].second-sq[last].first;
            int dd2=st[i].second-sq[last].second;
            int q=st[i].first-last;
            double x1= -1.0*dd1/q;
            double x2=-1.0*dd2/q;
            double y1= st[i].first*x1+st[i].second;
            double y2=st[i].first*x2+st[i].second;
            if(count==0){
                l=r=x1;
                u=d=y1;
            }
                if(x1>r)r=x1;
                if(x1<l)l=x1;
                if(y1>u)u=y1;
                if(y1<d)d=y1;
                if(x2>r)r=x2;
                if(x2<l)l=x2;
                if(y2>u)u=y2;
                if(y2<d)d=y2;
        
            count++;
        }
        if(!count)return 0;
        else return fabs(u-d)*fabs(l-r);
    }
};