解題報告
題意:
n個插頭m個設備k種轉換器。求有多少設備無法插入。
思路:
定義源點和匯點,源點和設備相連,容量為1.
匯點和插頭相連,容量也為1.
插頭和設備相連,容量也為1.
可轉換插頭相連,容量也為inf(由于插頭有無限個)
#include <map> #include <queue> #include <cstdio> #include <vector> #include <cstring> #include <iostream> #include <algorithm> #define inf 99999999 using namespace std; int n,m,k,cnt,l[500],mmap[500][500],N[1000]; map<string,int >Map; int bfs() { memset(l,-1,sizeof(l)); queue<int>Q; Q.push(0); l[0]=0; while(!Q.empty()) { int u=Q.front(); Q.pop(); for(int i=0;i<=cnt;i++) { if(l[i]==-1&&mmap[u][i]) { l[i]=l[u]+1; Q.push(i); } } } if(l[cnt]>0)return 1; return 0; } int dfs(int x,int f) { if(x==cnt)return f; int a; for(int i=0;i<=cnt;i++) { if(mmap[x][i]&&l[i]==l[x]+1&&(a=dfs(i,min(f,mmap[x][i])))) { mmap[x][i]-=a; mmap[i][x]+=a; return a; } } return 0; } int main() { int i,j; string a,b; cin>>n; cnt=1; for(i=0;i<n;i++) { cin>>a; N[cnt]=1;//cha Map[a]=cnt++; } cin>>m; for(i=0;i<m;i++) { cin>>a>>b; N[cnt]=2;//she Map[a]=cnt++; if(Map[b]==0) { N[cnt]=3;//new1 Map[b]=cnt++; } int u=Map[a]; int v=Map[b]; mmap[u][v]=1; } cin>>k; for(i=0;i<k;i++) { cin>>a>>b; if(Map[a]==0) { N[cnt]=3; Map[a]=cnt++; } if(Map[b]==0) { N[cnt]=3; Map[b]=cnt++; } int u=Map[a]; int v=Map[b]; mmap[u][v]=inf; } for(i=1;i<cnt;i++) { if(N[i]==1) { mmap[i][cnt]=1; } if(N[i]==2) { mmap[0][i]=1; } } int ans=0,t; while(bfs()) while(t=dfs(0,inf)) ans+=t; cout<<m-ans<<endl; return 0; }
Time Limit: ?1000MS | ? | Memory Limit: ?65536K |
Total Submissions: ?13550 | ? | Accepted: ?4518 |
Description
Since the room was designed to accommodate reporters and journalists from around the world, it is equipped with electrical receptacles to suit the different shapes of plugs and voltages used by appliances in all of the countries that existed when the room was built. Unfortunately, the room was built many years ago when reporters used very few electric and electronic devices and is equipped with only one receptacle of each type. These days, like everyone else, reporters require many such devices to do their jobs: laptops, cell phones, tape recorders, pagers, coffee pots, microwave ovens, blow dryers, curling?
irons, tooth brushes, etc. Naturally, many of these devices can operate on batteries, but since the meeting is likely to be long and tedious, you want to be able to plug in as many as you can.?
Before the meeting begins, you gather up all the devices that the reporters would like to use, and attempt to set them up. You notice that some of the devices use plugs for which there is no receptacle. You wonder if these devices are from countries that didn't exist when the room was built. For some receptacles, there are several devices that use the corresponding plug. For other receptacles, there are no devices that use the corresponding plug.?
In order to try to solve the problem you visit a nearby parts supply store. The store sells adapters that allow one type of plug to be used in a different type of outlet. Moreover, adapters are allowed to be plugged into other adapters. The store does not have adapters for all possible combinations of plugs and receptacles, but there is essentially an unlimited supply of the ones they do have.
Input
characters. No two devices will have exactly the same name. The plug type is separated from the device name by a space. The next line contains a single positive integer k (1 <= k <= 100) indicating the number of different varieties of adapters that are available. Each of the next k lines describes a variety of adapter, giving the type of receptacle provided by the adapter, followed by a space, followed by the type of plug.
Output
Sample Input
4 A B C D 5 laptop B phone C pager B clock B comb X 3 B X X A X D
Sample Output
1
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