【同一直线最多点】 poj 1118+2606+2780

#include<iostream>
using namespace std;
#define N 700
struct point {int x,y;} pnt[N];
int main()
{
    int n,i,j,k,max,cnt;
    while(scanf("%d",&n)&&n)
    {
        for(i=0;i<n;i++)
        scanf("%d%d",&pnt[i].x,&pnt[i].y);
        max=0;
        for(i=0;i<n;i++)
        for(j=i+1;j<n;j++)
        {
            cnt=0;
            for(k=j+1;k<n;k++)
            {
                if(k==i||k==j) continue;
                int left=(pnt[i].x-pnt[k].x)*(pnt[j].y-pnt[k].y);
                int right=(pnt[j].x-pnt[k].x)*(pnt[i].y-pnt[k].y);
                if(left==right) cnt++;
            }
            max=max>cnt? max:cnt;
        } 
        printf("%d\n",max+2);
    }
    return 0;
}

#include <iostream>
#include <cstdio>
#include <memory.h>
using namespace std;
const int maxn=202;
struct point
{
    int x;
    int y;
} pnt[maxn];
int main()
{
    //freopen("in.txt","r",stdin);
    int n,max,cnt;
    while(cin >> n)
    {
        memset(pnt,0,sizeof(pnt));
        for(int i=0;i<n;i++)
        {
            scanf("%d%d",&pnt[i].x,&pnt[i].y);
        }
        max=0;
        for(int i=0;i<n;i++)
        {
            for(int j=i+1;j<n;j++)
            {
                cnt=0;
                for(int k=j+1;k<n;k++)
                {
                    if(k==i || k==j)continue;
                    int left=(pnt[i].x-pnt[k].x)*(pnt[j].y-pnt[k].y);
                    int right=(pnt[j].x-pnt[k].x)*(pnt[i].y-pnt[k].y);
                    if(left==right)cnt++;
                }
                 if(cnt>max)max=cnt;
            }
        }
        cout << max+2 << endl;
    }
    return 0;
}
 
 

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
const int maxn = 1002;
const double eps = 1e-6;
struct point
{
    int x,y;
}node[maxn];
double k[maxn];
int n;
bool equal(double x,double y)
{
    if(abs(x-y) <= eps)
    {
        return true;
    }
    return false;
}
int max(int a,int b)
{
    return a > b ? a : b;
}
void read()
{
    for(int i=0;i<n;i++)
    {
        scanf("%d %d",&node[i].x,&node[i].y);
    }
    return;
}
void solve()
{
    int ans = 0;
    for(int i=0;i<n-1;i++)
    {
        int top = 0;
        int tmp = 0;
        for(int j=i+1;j<n;j++)
        {
            if(node[i].x == node[j].x)
            {
                tmp++;
            }
            else
            {
                k[top++] = (double)(node[j].y - node[i].y) / (node[j].x - node[i].x);
            }
        }
        sort(k,k+top);
        int cnt = 1;
        for(int j=0;j<top;j++)
        {
            if(j < top-1 && equal(k[j],k[j+1]))
            {
                cnt++;
            }
            else
            {
                tmp = max(tmp , cnt);
                cnt = 1;
            }
        }
        ans = max(ans , tmp);
    }
    printf("%d\n",ans+1);
    return;
}
int main()
{
    while(~scanf("%d",&n))
    {
        read();
        solve();
    }
    return 0;
}

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <memory.h>
using namespace std;
const int maxn=1002;
double s[500000+500];
struct location_
{
    int x;
    int y;
}l[maxn];
double slope(int m,int n)
{
    double ans=(double)(l[m].y-l[n].y)/(double)(l[m].x-l[n].x);
    return ans;
}
int main()
{
    //freopen("in.txt","r",stdin);
    int n;
    while(cin >> n)
    {
        memset(l,0,sizeof(l));
        memset(s,0.0,sizeof(s));
        int k=-1;
        int slo_cnt=0;
        for(int i=1;i<=n;i++)
        {
            scanf("%d%d",&l[i].x,&l[i].y);
        }
        for(int i=1;i<=n-1;i++)
        {
            for(int j=i+1;j<=n;j++)
            {
                if((l[i].x!=l[j].x))
                {
                    k++;
                    s[k]=slope(i,j);
                }
                else
                slo_cnt++;
            }
        }
        for(int i=2;i<=10000;i++)
        {
            if(i*(i-1)/2==slo_cnt)
            {
                slo_cnt=i;
                break;
            }
        }
//        cout << slo_cnt << ">>"<< endl;
//        for(int i=0;i<=k-1;i++)
//        {
//            cout << i << ‘ ‘ <<s[i] << endl;
//        }
        sort(s,s+k);
//        for(int i=0;i<=k-1;i++)
//        {
//            cout << i << ‘ ‘ <<s[i] << endl;
//        }
        int cnt=0;
        int max=0;
        for(int i=1;i<=k-1;i++)
        {
            if(fabs(s[i]-s[i-1])<=0.00000001)
            {
                cnt++;
                if(max<cnt)max=cnt;
            }
            else cnt=0;
        }
        max++;
//        cout << "dsdsdsds"<< "   " <<max << endl;
        for(int i=2;i<=10000;i++)
        {
            if(i*(i-1)/2==max)
            {
                max=i;
                break;
            }
        }
//        cout  << max<<"   max  " << endl;
//        cout << slo_cnt << " slo_cnt "<<endl;
        if(slo_cnt>max)max=slo_cnt;
        cout << max << endl;
    }
    return 0;
}