Beginner KD Tree

In the beginning will not KD tree, feel kd tree must be very God, learned kd tree found KD tree is very good to write.

Each node of the KD tree has a split hyper-plane, and I am dividing the current dimension with a depth% dimension, compared to the current node.

Attach template code, find plane K close-up (kd tree bare title)

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <algorithm>5#include <queue>6#include <cmath>7 using namespacestd;8 #defineMAXN 1000209 #defineINF 0X3F3F3F3F3F3F3FLLTen  One intNow ; AtypedefLong Longll; - structpoint{ -     intx[2]; the     BOOL operator< (point a)Const{ -         returnX[now] <A.x[now]; -     } - }A[MAXN]; +Priority_queue <ll>Heap; - intN,k,id; + ll Curd; A  at voidBuildintLintRintDEP) { -     if(L > R)return; -now = dep%2; -     intMid = (L + r) >>1; -Nth_element (A + l,a + mid,a + R +1); -Build (L,mid-1, DEP +1); inBuild (Mid +1, R,DEP +1); - } toinline LL Sqr (intx) {return(LL) x *x;} +inline ll Dis (intX1,intX2,intY1,inty2) { -     returnSqr (X1-X2) + sqr (y1-y2); the } * voidQuery (point P,intLintRintDEP) { $     if(L > R)return;Panax Notoginsengnow = dep%2; -     intMid = (L + r) >>1; thell tmp = DIS (p.x[0],a[mid].x[0],p.x[1],a[mid].x[1]); +     if(Mid >ID) { A         if(Heap.size () <k) Heap.push (TMP); the         Else if(Heap.top () >tmp) {Heap.pop (); Heap.push (TMP);} +     } -     if(L = = r)return; $     if(P.x[now] >A[mid].x[now]) { $Query (P,mid +1, R,DEP +1); -now = dep%2; -         if(Heap.size () < K | | heap.top () >= Sqr (P.x[now]-a[mid].x[now]) query (P,l,mid-1, DEP +1); the     } -     Else{WuyiQuery (P,l,mid-1, DEP +1); thenow = dep%2; -         if(Heap.size () < K | | heap.top () >= Sqr (P.x[now]-a[mid].x[now]) query (P,mid +1, R,DEP +1); Wu     } - } About intMain () { $Freopen ("star.in","R", stdin); -Freopen ("Star.out","W", stdout); -scanf"%d%d",&n,&k); -      for(inti =1; I <= N; i++){ Ascanf"%d%d", &a[i].x[0],&a[i].x[1]); +     } theBuild1N1); -      for(inti =1; I <= N; i++){ $ID =i; theQuery (A[i],1N1); the     } theprintf"%lld\n", Heap.top ()); the     return 0; -}

After learning more about the application of KD tree, the type of problem can be applied in KD tree model.

Beginner KD Tree