poj 1548

来源：互联网发布：杨幂网络暴力事例编辑：程序博客网时间：2024/04/30 02:46
最小路径覆盖 = n - 最大匹配
能从a走到b,就连一条有向边
//tpl//ipqhjjybj_tpl.h//header.h#include <cstdio>#include <cstdlib>#include <map>#include <set>#include <algorithm>#include <cstring>#include <iostream>#include <vector>#include <string>#define mp(x,y) make_pair(x,y)#define pii pair<int,int>#define pLL pair<long long ,long long>#define rep(i,j,k) for(int i = j; i < k;i++)#define repn(i,j,k) for(int i = j; i <= k;i++)using namespace std;const int INF = 0x3f3f3f3f;const int N = 1300;int g[N][N];int cx[N],cy[N];int mark[N];int nx,ny;int dfs(int u)  {      rep(v,0,ny)     {          if(g[u][v]&&!mark[v])//u和v不要搞反了          {              mark[v]=1;              if(cy[v]==-1||dfs(cy[v]))              {                  cx[u]=v;                  cy[v]=u;                  return 1;              }          }      }      return 0;  }  int maxmatch()  {      int res=0;      memset(cx,-1,sizeof(cx));      memset(cy,-1,sizeof(cy));      rep(i,0,nx)    {          if(cx[i]==-1)          {              memset(mark,0,sizeof(mark));              res+=dfs(i);          }      }      return res;  }  int x,y;map<pii,int> M;vector<pii >pm; int getNum(int x,int y){if(M.count(mp(x,y))){return M[mp(x,y)];}pm.push_back(mp(x,y));return M[mp(x,y)] = pm.size()-1;}int main(){while(scanf("%d %d",&x,&y)!=EOF){if(x==-1 && y == -1) break;M.clear() , pm.clear();memset(g,0,sizeof(g));int n ;getNum(x,y);while(scanf("%d %d",&x,&y)!=EOF){if(x==0 && y==0) break;getNum(x,y);}n = pm.size();rep(i,0,n){<span style="white-space:pre"></span>rep(j,0,n){<span style="white-space:pre"></span>if(i!=j)<span style="white-space:pre"></span>if(pm[i].first <=pm[j].first && pm[i].second <= pm[j].second){<span style="white-space:pre"></span>g[i][j] = 1;<span style="white-space:pre"></span>}<span style="white-space:pre"></span>}<span style="white-space:pre"></span>}nx = ny = n;int ans = maxmatch();printf("%d\n",n-ans);}return 0;}
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