poj2002 数正方形 hash

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直接上渣代码了

#include <iostream>using namespace std;struct gtype {       int x,y,next;}g[3000];int first[1000100],tot,n,x[3010],y[3010],ans,h,tx,ty;int hash(int x,int y) {    return (40000*x+y+800040000)%999991+1;}bool find(int x,int y) {     int h = hash(x,y);     bool f = false;     for (int t=first[h];t!=-1;t=g[t].next)         if (g[t].x==x && g[t].y==y) {                 f = true;            break;         }      return f;}int main() {    while (~scanf("%d",&n)) {          tot = 0;          memset(first,-1,sizeof(first));          for (int i=1;i<=n;i++) {              scanf("%d%d",&x[i],&y[i]);              h = hash(x[i],y[i]);              tot++;              g[tot].x = x[i];              g[tot].y = y[i];              g[tot].next = first[h];              first[h] = tot;          }          ans = 0;          for (int i=1;i<=n;i++)              for (int j=i+1;j<=n;j++) {                  if (i==j) continue;                  tx = x[i]-x[j];                  ty = y[i]-y[j];                  if (find(x[i]+ty,y[i]-tx) && find(x[j]+ty,y[j]-tx)) ans++;                  if (find(x[i]-ty,y[i]+tx) && find(x[j]-ty,y[j]+tx)) ans++;              }          printf("%d\n",ans/4);    }    return 0;}