Space Ant 極角排序

題意：給定n個點，任意兩點不在一個x軸和y軸上，輸出一條能經過最多點的路線，就下面這圖，每次只能左轉，實際就是外面一圈包進去，

選擇一個最外側點，對剩下點做極角排序，一個個點選下去。能保證每個點都經過。

 

 

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<string.h>
#include<iomanip>
#include<limits.h>
#include<algorithm>
#include<deque>
#include<functional>
#include<iterator>
#include<vector>
#include<list>
#include<map>
#include<memory>
#include<numeric>
#include<queue>
#include<set>
#include<stack>
#include<utility>
using namespace std;
#define mp make_pair
#define ss second
#define ff first
#define pb push_back
template <class T>
void read(T &x)
{
    static char ch;
    bool neg = false;
    while(!isdigit(ch = getchar())) (ch == '-') && (neg = true);
    for(x = ch - '0'; isdigit(ch = getchar()); x = x * 10 + ch - '0');
    (neg) &&(x = -x);
}
template<class T, class... U> void read(T &head, U &... tail){read(head), read(tail...);}
typedef long long ll;
typedef unsigned long long ull;
const int inf = 0x3f3f3f3f;
const int maxn = 105;
int n,m;
struct P
{
    double x, y;
    int ind;
} v[maxn];
bool vis[maxn];
double compare(P a, P b, P c)
{
    return (b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y);
}
P c;
bool cmp(P a, P b)
{
    if(compare(c, a, b) == 0)
        return a.x < b.x;
    else
        return compare(c, a, b) > 0;
}
bool cmp1(P a,P b)
{
    return a.y<b.y;
}
std::vector<P> w;
std::vector<int> q;
void slove()
{
    c=w[0];
    q.push_back(c.ind);
    vis[c.ind]=true;
    w.clear();
    for(int i=1;i<n;i++)
    {
        if(!vis[v[i].ind])
        w.push_back(v[i]);
    }
    if(w.size()==0) return;
    sort(w.begin(),w.end(),cmp);
    slove();
}
void work()
{
    read(n);
    q.clear();
    w.clear();
    memset(vis,false,sizeof vis);
    for(int i=0;i<n;i++) 
        scanf("%d %lf %lf",&v[i].ind,&v[i].x,&v[i].y);
    sort(v,v+n,cmp1);
    c=v[0];
    q.push_back(c.ind);
    vis[c.ind]=true;
    for(int i=1;i<n;i++)
    {
        if(!vis[v[i].ind])
        w.push_back(v[i]);
    }
    sort(w.begin(),w.end(),cmp);  
    
    slove();
    printf("%d",n);
    for(int i=0;i<n;i++)
        printf(" %d",q[i]);
    printf("\n");


}

int main()
{
    int T;read(T);while(T--)
    //while(~scanf("%d", &n))
    work();
}