bzoj1173: [Balkan2007]point

Description

Gives a point on n three-dimensional space. Ask how many straight lines there are at least three points in the line.

Input

The first line gives the number of characters n,n under [4,1000] n lines, three digits per line, to describe the coordinates of the point, whose value is in [ -10000,10000]

Output

How many lines are there?

Enumerates the direction of the line, constructs a graph for each direction, if the two points between lines in this direction is connected to the edge, each of at least three points of the Unicom block represents a straight line

#include <cstdio>#include<algorithm>inlineintgcdintXinty) {     for(intz;y;z=x,x=y,y=z%y); returnx;}intN;structpos{intx, Y, Z voidfix () {intg=gcd (gcd (x, y), z); X/=g;y/=g;z/=G; if(x!=0?x<0: y!=0?y<0:z<0) x=-x,y=-y,z=-Z; }}ps[1007];BOOL operator==(ConstPos&a,ConstPOS&AMP;B) {returna.x==b.x&&a.y==b.y&&a.z==b.z;}BOOL operator< (ConstPos&a,ConstPOS&AMP;B) {returna.x!=b.x?a.x<b.x:a.y!=b.y?a.y<b.y:a.z<b.z;} POSoperator-(POS A,pos b) {return(POS) {a.x-b.x,a.y-b.y,a.z-b.z};}structline{intb; Pos v;} as[1007*555];BOOL operator< (ConstLine&a,ConstLINE&AMP;B) {returna.v<B.V;}intap=0, ans=0;intes[1000007],enx[1000007],e0[1007],ep=2, ds[1007],dp=0, t,tk[1007];intDfsintW) {    intC=1; TK[W]=T;  for(intI=e0[w];i;i=Enx[i]) {        intu=Es[i]; if(tk[u]!=t) c+=dfs (U); }    returnC;}voidAdde (intAintb) {    if(!e0[a]) ds[dp++]=A; if(!e0[b]) ds[dp++]=b; ES[EP]=b;enx[ep]=e0[a];e0[a]=ep++; ES[EP]=a;enx[ep]=e0[b];e0[b]=ep++;}intMain () {scanf ("%d",&N);  for(intI=1; i<=n;++i) scanf ("%d%d%d",&ps[i].x,&ps[i].y,&ps[i].z);  for(intI=1; i<=n;++i) {         for(intj=1; j<i;++j) {            ( as[Ap++]= (line) {i,j,ps[i]-Ps[j]}).        V.fix (); }} std::sort ( as, as+AP);  for(intI=0, j=0;i<ap;) { for(;j<ap&& as[i].v== as[j].v;++j);  for(++t;i<j;++i) Adde ( as[I].a, as[i].b];  for(intk=0; k<dp;++k)if(Dfs (ds[k]) >=3)++ans;  while(DP) e0[ds[--dp]]=0; ep=2; } printf ("%d\n", ans); return 0;}

bzoj1173: [Balkan2007]point