Ural 1099. work scheduling

General Graph Matching with a flower tree template question:

Compress the ring into a circle (blossom), and then find the augmented path .....

1099. Work schedulingtime limit: 0.5 second
Memory limit: 64 MB
There is certain amount of night guards that are available to protect the local junkyard from possible junk robberies. these guards need to scheduled in pairs, so that each pair guards at different night. the junkyard CEO ordered you to write a program which given the guards characteristics determines the maximum amount of scheduled guards (the rest will be fired ). please note that each guard can be scheduled with only one of his colleagues and no guard can work alone. inputthe first line of the input contains one number N≤0. 222 which is the amount of night guards. unlimited number of lines consisting of unordered pairs ( I, J) Follow, each such pair means that guard # IAnd guard # JCan work together, because it is possible to find uniforms that suit both of them (the junkyard uses different parts of uniforms for different guards I. e. helmets, pants, jackets. it is impossible to put small helmet on a guard with a big head or big shoes on guard with small feet ). the input ends with EOF. outputyou shoshould output one possible optimal assignment. on the first line of the output write the even number C, The amount of scheduled guards. Then output C/2 lines, each containing 2 integers ( I, J) That denote that IAnd JWill work together. Sample

Input	Output
31 22 31 3	21 2

Problem Author:Jivko Ganev
Tags:Graph Theory () Difficulty: 1356 printable version submit solution discussion (51)
My submissions all submissions (15804) all accepted submissions (1687) solutions rating (610)

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <queue>using namespace std;const int maxn=250;/*******************************************/struct Edge{  int to,next;}edge[maxn*maxn];int Adj[maxn],Size;void init(){  memset(Adj,-1,sizeof(Adj)); Size=0;}void add_edge(int u,int v){  edge[Size].to=v; edge[Size].next=Adj[u]; Adj[u]=Size++;}/*******************************************/int n;int Match[maxn];bool G[maxn][maxn];int Start,Finish,NewBase;int Father[maxn],Base[maxn];bool InQueue[maxn],InPath[maxn],InBlossom[maxn];int Count;queue<int> q;int FindCommonAncestor(int u,int v){  memset(InPath,false,sizeof(InPath));  while(true)    {      u=Base[u];      InPath[u]=true;      if(u==Start) break;      u=Father[Match[u]];    }  while(true)    {      v=Base[v];      if(InPath[v]) break;      v=Father[Match[v]];    }  return v;}void ResetTrace(int u){  int v;  while(Base[u]!=NewBase)    {      v=Match[u];      InBlossom[Base[u]]=InBlossom[Base[v]]=true;      u=Father[v];      if(Base[u]!=NewBase) Father[u]=v;    }}void BlosomContract(int u,int v){  NewBase=FindCommonAncestor(u,v);  memset(InBlossom,false,sizeof(InBlossom));  ResetTrace(u);  ResetTrace(v);  if(Base[u]!=NewBase) Father[u]=v;  if(Base[v]!=NewBase) Father[v]=u;  for(int tu=1;tu<=n;tu++)    {      if(InBlossom[Base[tu]])        {          Base[tu]=NewBase;          if(!InQueue[tu])            {              q.push(tu);              InQueue[tu]=true;            }        }    }}void FindAugmentingPath(){  memset(InQueue,false,sizeof(InQueue));  memset(Father,0,sizeof(Father));  for(int i=1;i<=n;i++)    Base[i]=i;  while(!q.empty()) q.pop();  q.push(Start); InQueue[Start]=true;  Finish=0;  while(!q.empty())    {      int u=q.front(); //InQueue[u]=false;      q.pop();      for(int i=Adj[u];~i;i=edge[i].next)        {          int v=edge[i].to;          if((Base[u]!=Base[v])&&Match[u]!=v)            {              if(v==Start||(Match[v]>0&&Father[Match[v]]>0))                BlosomContract(u,v);              else if(Father[v]==0)                {                  Father[v]=u;                  if(Match[v]>0)                    {                      q.push(Match[v]);                      InQueue[Match[v]]=true;                    }                  else                    {                      Finish=v;                      return ;                    }                }            }        }    }}void AugmentPath(){  int u,v,w;  u=Finish;  while(u>0)    {      v=Father[u];      w=Match[v];      Match[v]=u;      Match[u]=v;      u=w;    }}void Edmonds(){  memset(Match,0,sizeof(Match));  for(int u=1;u<=n;u++)    {      if(Match[u]==0)        {          Start=u;          FindAugmentingPath();          if(Finish>0) AugmentPath();        }    }}void PrintMatch(){  Count=0;  for(int i=1;i<=n;i++)    {      if(Match[i]) Count++;    }  printf("%d\n",Count);  for(int u=1;u<=n;u++)    {      if(u<Match[u])        printf("%d %d\n",u,Match[u]);    }}int main(){  //freopen("data.in","r",stdin);  while(scanf("%d",&n)!=EOF)    {      init();      memset(G,false,sizeof(G));      int u,v;      while(scanf("%d%d",&u,&v)!=EOF)        {          if(G[u][v]==true) continue;          G[u][v]=G[v][u]=true;          add_edge(u,v);          add_edge(v,u);        }      Edmonds();      PrintMatch();    }  return 0;}

Ural 1099. work scheduling