POJ 1741 tree divide and conquer (point divide and cure template problem)

POJ 1741

Test Instructions : Ask for the number of points in a tree to <=k.

Summary : Point division Treatment, do not understand. I probably knocked it over.

#include <iostream>#include<cstdio>#include<cstdlib>#include<algorithm>#include<cstring>#include<string>#include<cmath>#include<queue>#include<stack>#include<map>#include<bitset>#include<vector>#include<Set>using namespacestd;#pragmaComment (linker, "/stack:102400000,102400000")#defineF (I,A,B) for (int i=a;i<b;i++)#defineFF (I,A,B) for (int i=a;i<=b;i++)#defineMes (A, b) memset (A,b,sizeof (a))#defineINF 0x3f3f3f3ftypedefLong Longll;Const intN = 1e5+ -;intN, K, ans, root, num, maxn;intVis[n], Size[n], dis[n], maxv[n];//size[] Indicates the number of sub-tree nodes, maxv[] represents the maximum number of subtrees, dis[] represents the node to the center of gravity distanceintHead[n], E;structEdge {intV,next,w;} Edge[n];voidInit () {ans=e=0; Mes (head,-1); Mes (Vis,0);}voidAddedge (intUintVintW) {EDGE[E].V=v; EDGE[E].W=W; Edge[e].next=Head[u]; Head[u]=e++;}voidDfssize (intUintFa//calculate the number of nodes in a U-tree{Size[u]=1; maxv[u]=0;  for(intI=head[u]; i!=-1; I=Edge[i].next) {        intv=edge[i].v; if(V!=fa && vis[v]==0) {dfssize (V, u); Size[u]+=Size[v]; if(Size[v]>maxv[u]) maxv[u]=size[v];//find the maximum number of subtrees        }    }}voidDfsroot (intRintUintFa//Calculate the center of gravity of the U-Tree after removing the R tree, reduce the complexity, it seems to use the tree-shaped dp;r as the center of gravity of the tree{    if(Size[r]-size[u] >maxv[u]) maxv[u]=size[r]-size[u];//if the U-tree node is less than the number of U-trees removed by the R-Tree, the U-tree is reversed to remove the node from the U-Tree as a subtree    if(MAXV[U]&LT;MAXN) maxn=maxv[u], root=u;//MAXV is the maximum number of subtrees, Root is the center of gravity     for(intI=head[u]; i!=-1; I=Edge[i].next) {        intv=edge[i].v; if(V!=fa && vis[v]==0) Dfsroot (r,v,u); }}voidDfsdis (intUintDintFa//calculate the distance from each node in the U tree to the center of gravity{dis[num++]=D;  for(intI=head[u]; i!=-1; I=Edge[i].next) {        intv=edge[i].v; if(V!=fa && vis[v]==0) Dfsdis (V, d+edge[i].w, u); }}intCalcintUintD//calculate the number of point-to-dis () <=k in the U-Tree{    intret=0; Num=0;//num represents the number of points in the U-TreeDfsdis (U,d,0); Sort (dis, dis+num); intI=0, j=num-1;  while(I&LT;J) {//Classic, opposite search         while(dis[i]+dis[j]>k && i<j) j--; RET+ = Ji; I++; }    returnret;}voidDfsintu) {MAXN=N; Dfssize (U,0); Dfsroot (U,u,0);//find the center of gravity root in the U treeans+= Calc (Root,0); Vis[root]=1;  for(intI=head[root]; i!=-1; I=edge[i].next) {//from the center of gravity, remove the center of gravity, and then search the sub-tree        intv=edge[i].v; if(vis[v]==0) {ans-= Calc (v, EDGE[I].W);//minus the V subtree, because the DFS (v) below also addsDfs (v); }    }}intMain () { while(~SCANF ("%d%d", &n,&k) && (n&&k)) {Init (); intu,v,l; FF (i,1, N-1) {scanf ("%d%d%d", &u,&v,&l);            Addedge (u,v,l);        Addedge (v,u,l); } DFS (1); printf ("%d\n", ans); }    return 0;}

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POJ 1741 tree divide and conquer (point divide and cure template problem)