CH Round#48 T1数三角形

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真是跪烂……我叉积判完了三点共线还去判了三边长的关系……实际上不共线的话三边长关系肯定是满足的……于是因为精度设置问题挂掉了……（我设个1e-12么还有机会，1e-6肯定挂了……）

#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>#include<vector>#include<string>#include<set>#include<queue>#include<stack>#include<map>#include<cmath>#include<cstdlib>#define ll long long#define maxn 100010#define inf 1000000000#define linf (1LL<<50)using namespace std;inline ll read(){    ll x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x*=10;x+=ch-'0';ch=getchar();}    return x*f;}inline void read(char *s,int &ts){char x=getchar();while(!(x>='a'&&x<='z'))x=getchar();while(x>='a'&&x<='z')s[++ts]=x,x=getchar();}int ans=0;int n;int x[maxn],y[maxn];double f(int a,int b){    return sqrt((x[b]-x[a])*(x[b]-x[a])+(y[b]-y[a])*(y[b]-y[a]));}int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++)    scanf("%d%d",&x[i],&y[i]);    for(int i=1;i<=n-2;i++)    for(int j=i+1;j<=n-1;j++)    for(int k=j+1;k<=n;k++)    if((y[j]-y[i])*(x[k]-x[j])!=(y[k]-y[j])*(x[j]-x[i])) ans++;    printf("%d\n",ans);    return 0;}

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