Hdu 6203 Ping Ping Ping (greedy + tree-like array +dfs order)

Topic Link: hdu 6203 ping Ping Ping

Test instructions

Give you a tree n+1 tree, there is now a Q-path does not pass, ask you at least how many nodes broken down.

Exercises

Consider the greedy, the Q path to the LCA, according to the depth of the LCA from large to small sort.

Then for each path, see if x or Y is in a subtree that has been banned, and if not, then ans++, mark the subtrees Tree of LCA (x, y) as forbidden.

1#include <bits/stdc++.h>2 #defineF (I,A,B) for (int i= (a); i<= (b); ++i)3 #defineMST (A, B) memset (A,b,sizeof (a))4 using namespacestd;5 6 Const intn=1e4+7;7 intT,n,m,sum[n];8 intnxt[2*n],g[n],v[2*n],ed,x,y;9 intHs[n],fa[n],top[n],dep[n],sz[n],dfsl[n],dfsr[n],idx;Ten  One voidAdgintXintY) {v[++ed]=y,nxt[ed]=g[x],g[x]=Ed;}  A  - voidDFS1 (intUintpre) { -dfsl[u]=++idx,dep[u]=dep[pre]+1, hs[u]=0, fa[u]=pre,sz[u]=1; the      for(intI=g[u];i;i=nxt[i])if(v[i]!=pre) -DFS1 (V[i],u), sz[u]+=sz[v[i]],hs[u]= (Sz[v[i]]>sz[hs[u])?V[i]:hs[u]; -dfsr[u]=idx; - } + voidDFS2 (intUintTP) { -top[u]=TP; +     if(Hs[u]) DFS2 (HS[U],TP); A      for(intI=g[u];i;i=Nxt[i]) at     if(v[i]!=fa[u]&&v[i]!=Hs[u]) DFS2 (V[i],v[i]); - } -  - intLCA (intXinty) - { -      while(top[x]!=Top[y]) indep[top[x]]>dep[top[y]]?x=fa[top[x]]:y=Fa[top[y]]; -     returnDep[x]<dep[y]?x:y; to } +  -InlinevoidAddintXintc) { while(x<=n) sum[x]+=c,x+=x&-x;} theInlineintAskintx) {intan=0; while(x) an+=sum[x],x-=x&-x;returnan ;} *  $ structNodePanax Notoginseng { -     intX,y,lca,val; theNode (intA=0,intb=0,intC=0,intD=0): X (a), Y (b), LCA (c), Val (d) {} +     BOOL operator< (ConstNode &b)Const{returnVal>B.val;} A}q[n*5]; the  + intMain () { -      while(~SCANF ("%d",&N)) $     { $MST (G,0), MST (SUM,0), ed=0; -F (I,1, N) -         { thescanf"%d%d",&x,&y); -x++,y++;Wuyi ADG (x, y), ADG (y,x); the         } -n++,idx=0, DFS1 (1,0), DFS2 (1,1); Wuscanf"%d",&m); -F (I,1, M) About         { $scanf"%d%d",&x,&y); -x++,y++; -             intLca=LCA (x, y); -q[i]=Node (X,y,lca,dep[lca]); A         } +Sort (q+1, q+1+m); the         intans=0; -F (I,1, M) $         { the             intFlag= (Ask (dfsl[q[i].x) | |ask (Dfsl[q[i].y])); the             if(!flag) the             { theans++; -Add (Dfsl[q[i].lca],1); inAdd (dfsr[q[i].lca]+1,-1); the             } the         } Aboutprintf"%d\n", ans); the     } the     return 0; the}

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Hdu 6203 Ping Ping Ping (greedy + tree-like array +dfs order)