# Uvalive 3523 Knight of Round table Round Table Knight (undirected graph-point dual-connected component)

Source: Internet
Author: User

Because the knight who hates each other cannot be adjacent, the knight can be connected to the non-side, the meeting request is odd, the problem is to seek no more than the number of nodes on a simple odd circle.

Tarjan directly set previously written, the result is wrong, to pay special attention to the side to join the stack of time ... I don't understand the algorithm.

`#include <bits/stdc++.h>using namespacestd;#defineBug (x) cout<< #x << ' = ' <<x<<endl;Const intMAXV = ++5;Const intMaxe = MAXV*MAXV;//Open Smallintdfn[maxv],low[maxv],bccno[maxv],dfs_clock,bcc_cnt;BOOLIscut[maxv];vector<int>BCC[MAXV];inthead[maxv],fro[maxe],to[maxe],nxt[maxe],ecnt;intEdges[maxe],top;voidAddedge (intUintv) {fro[ecnt]=u; TO[ECNT]=v; NXT[ECNT]=Head[u]; Head[u]= ecnt++;}voidTarjan (intUintFA) {Dfn[u]= Low[u] = + +Dfs_clock;  for(inti = Head[u]; ~i; i =Nxt[i]) {        intv =To[i]; if(!Dfn[v]) {edges[++top] =i;            Tarjan (V,i); Low[u]=min (low[v],low[u]); if(Low[u] >=Dfn[u]) {Iscut[u]=true; Bcc_cnt++; Bcc[bcc_cnt].clear ();//bcc starting from 1                intu,v;  Do{                    intE = edges[top--]; U= Fro[e], V =To[e]; if(Bccno[u]! = bcc_cnt) {Bcc[bcc_cnt].push_back (U); bccno[u]=bcc_cnt;} if(Bccno[v]! = bcc_cnt) {Bcc[bcc_cnt].push_back (V); bccno[v]=bcc_cnt;} } while(u!=u| | v!=v); }        }Else  if((i^1)! = FA && Dfn[v] < Dfn[u]) {Low[u] = min (low[u],dfn[v]); Edges[++top] = i; }//= = higher than ^ priority! The second condition is less, what's the reason for WA ?    }}voidFIND_BCC (intN) {Top=0; memset (DFN,0,sizeof(DFN)); memset (Iscut,0,sizeof(Iscut)); memset (Bccno,0,sizeof(BCCNO)); Dfs_clock= BCC_CNT =0;  for(inti =0; I < n; i++) {        if(!Dfn[i]) {Tarjan (i,-1); Iscut[i]= ~nxt[head[i]];// ! (Nxt[head[i]] = =-1);//Tree Ghent, if there is only one child node false        }    }}intCOLOR[MAXV];BOOLBipartite (intUintBB) {     for(inti = Head[u]; ~i; i =Nxt[i]) {        intv = to[i];if(Bccno[v]! = b)Continue; if(Color[v] = = Color[u])return false; if(!Color[v]) {Color[v]=3-Color[u]; if(!bipartite (V,B))return false; }    }    return true;}BOOLHATE[MAXV][MAXV];BOOLINODD[MAXV];intMain () {//freopen ("In.txt", "R", stdin);    intn,m;  while(~SCANF ("%d%d", &n,&m) && (n| |m)) {memset (hate,0,sizeof(hate));  while(m--){            intU,v; scanf"%d%d", &u,&v); U--, v--; HATE[U][V]= Hate[v][u] =true; } memset (Head,-1,sizeof(head)); ECNT =0;  for(inti =0; I < n; i++)         for(intj = i+1; J < N; J + +)if(!Hate[i][j])        {Addedge (i,j); Addedge (j,i);       } FIND_BCC (n); //bug (bcc_cnt);memset (Inodd,0,sizeof(inodd));  for(inti =1; I <= bcc_cnt; i++) {memset (color,0,sizeof(color));  for(intj =0; J < Bcc[i].size (); J + +) Bccno[bcc[i][j]] = i;//cut points, which belong to multiple connected components, so special handling            intU = bcc[i][0]; Color[u]=1; if(!bipartite (u,i)) {                 for(intj =0; J < Bcc[i].size (); J + +) Inodd[bcc[i][j]] =true; }        }        intAns =N;  for(intI=0; I < n; i++)if(Inodd[i]) ans--; printf ("%d\n", ans); }    return 0;}`

Uvalive 3523 Knight of Round table Round Table Knight (undirected graph-point dual-connected component)

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