题目:http://www.lydsy.com/JudgeOnline/problem.php?id=2338
中学数学老师告诉我们,一个矩形的两条对角线相等,所以只要把所有的边拿出来,记录下中点坐标及长度,然后排一遍序扫一遍更新答案。。(听说开double会炸?
#include<cstring> #include<cstdio> #include<algorithm> #include<cmath> #include<iostream> #include<queue> #define rep(i,l,r) for (int i=l;i<=r;i++) #define down(i,l,r) for (int i=l;i>=r;i--) #define clr(x,y) memset(x,y,sizeof(x)) #define maxn 1505 #define inf int(1e9) #define eps 1e-6 using namespace std; typedef long long ll; struct data{ll len,x,y;int a,b; }a[maxn*maxn]; struct node{ll x,y; }; int n,cnt,next,now; ll ans,x[maxn],y[maxn]; ll read(){ ll x=0,f=1; char ch=getchar(); while (!isdigit(ch)) {if (ch==‘-‘) f=-1; ch=getchar();} while (isdigit(ch)) {x=x*10+ch-‘0‘; ch=getchar();} return x*f; } ll sqr(ll x){ return x*x; } ll dis(int a,int b){ return sqr(x[a]-x[b])+sqr(y[a]-y[b]); } bool cmp(data a,data b){ if (a.x==b.x&&a.len==b.len) return a.y<b.y; else if (a.len==b.len) return a.x<b.x; return a.len<b.len; } bool jud(data a,data b){ if (a.x==b.x&&a.y==b.y&&a.len==b.len) return 1; return 0; } ll cross(node p,node q){ return abs(p.x*q.y-p.y*q.x); } void solve(data a,data b){ node p=(node){x[a.a]-x[a.b],y[a.a]-y[a.b]}; node q=(node){x[a.a]-x[b.a],y[a.a]-y[b.a]}; ans=max(ans,cross(p,q)); } int main(){ scanf("%d",&n); rep(i,1,n){ x[i]=read(); y[i]=read(); } rep(i,1,n) rep(j,i+1,n) a[++cnt]=(data){dis(i,j),x[i]+x[j],y[i]+y[j],i,j}; sort(a+1,a+1+cnt,cmp); now=cnt; while (now>1){ next=now-1; while (jud(a[now],a[next])) { solve(a[now],a[next]); next--; } now--; } printf("%lld\n",ans); return 0; }
时间: 2024-10-12 13:05:44