网络流，设备、插头和转接器建图(简单map的应用)
题意：
给你n个插座，m个设备，每台设备都有对应的插座，有k个转接器。
要求：求满足不能插上插座的用电器最少个数
solution:
HINT：每种适配器都有无限个，所以建图的时候要改为INF。
答案为m-idnic()
1 #include<iostream> 2 #include<cstdio> 3 #include<algorithm> 4 #include<vector> 5 #include<queue> 6 #include<map> 7 #include<cstring> 8 #define mp make_pair 9 #define pb push_back 10 #define first fi 11 #define second se 12 #define pw(x) (1ll << (x)) 13 #define sz(x) ((int)(x).size()) 14 #define all(x) (x).begin(),(x).end() 15 #define rep(i,l,r) for(int i=(l);i<(r);i++) 16 #define per(i,r,l) for(int i=(r);i>=(l);i--) 17 #define FOR(i,l,r) for(int i=(l);i<=(r);i++) 18 #define eps 1e-9 19 #define PIE acos(-1) 20 #define cl(a,b) memset(a,b,sizeof(a)) 21 #define fastio ios::sync_with_stdio(false);cin.tie(0); 22 #define lson l , mid , ls 23 #define rson mid + 1 , r , rs 24 #define ls (rt<<1) 25 #define rs (ls|1) 26 #define INF 0x3f3f3f3f 27 #define LINF 0x3f3f3f3f3f3f3f3f 28 #define freopen freopen("in.txt","r",stdin); 29 #define cfin ifstream cin("in.txt"); 30 #define lowbit(x) (x&(-x)) 31 #define sqr(a) a*a 32 #define ll long long 33 #define ull unsigned long long 34 #define vi vector<int> 35 #define pii pair<int, int> 36 #define dd(x) cout << #x << " = " << (x) << ", " 37 #define de(x) cout << #x << " = " << (x) << "\n" 38 #define endl "\n" 39 using namespace std; 40 int n,m,k; 41 const int maxn=505; 42 map<string,int>ids; 43 44 struct Edge{ 45 int u,v,cap; 46 }; 47 int S,T; 48 vi G[maxn]; 49 int dep[maxn]; 50 vector<Edge> edge; 51 inline int id(string s) 52 { 53 int m=sz(ids); 54 if(ids.count(s))return ids[s]; 55 return ids[s]=m; 56 } 57 58 void addedge(int u,int v,int cap) 59 { 60 edge.pb((Edge){u,v,cap}); 61 edge.pb((Edge){v,u,0}); 62 int t=sz(edge); 63 G[u].pb(t-2); 64 G[v].pb(t-1); 65 } 66 67 bool bfs() 68 { 69 cl(dep,-1); 70 int Q[maxn]; 71 int h=0,t=1;dep[S]=0;Q[t]=S; 72 while(h<t){ 73 // de(T); 74 int x=Q[++h]; 75 if(x==T)return 1; 76 rep(i,0,sz(G[x])){ 77 Edge& e=edge[G[x][i]]; 78 // de(e.v);puts("here"); 79 if(dep[e.v]==-1&&e.cap){ 80 dep[e.v]=dep[x]+1; 81 Q[++t]=e.v; 82 } 83 } 84 } 85 return 0; 86 } 87 int dfs(int x,int f) 88 { 89 if(x==T)return f; 90 int used=0,t; 91 rep(i,0,sz(G[x])){ 92 Edge& e=edge[G[x][i]]; 93 // dd(e.u),de(e.v); 94 if(e.cap&&dep[e.v]==dep[x]+1){ 95 t=dfs(e.v,min(e.cap,f)); 96 e.cap-=t;edge[G[x][i]^1].cap+=t; 97 used+=t;f-=t; 98 if(!f)return used; 99 } 100 } 101 if(!used)dep[x]=-1; 102 return used; 103 } 104 int dinic() 105 { 106 int ans=0; 107 while(bfs())ans+=dfs(S,INF); 108 return ans; 109 } 110 void mapping() 111 { 112 S=0; 113 string in[maxn],out[maxn];id("S"); 114 cin>>n; 115 FOR(i,1,n)cin>>in[i]; 116 cin>>m; 117 FOR(i,n+1,n+m)cin>>in[i]>>out[i],addedge(0,id(in[i]),1),addedge(id(in[i]),id(out[i]),1); 118 cin>>k; 119 FOR(i,n+m+1,n+m+k)cin>>in[i]>>out[i],addedge(id(in[i]),id(out[i]),INF); 120 // FOR(i,1,n)dd(in[i]),de(id(in[i])); 121 T=n+m+k+1; 122 FOR(i,1,n)addedge(id(in[i]),T,1); 123 } 124 int main() 125 { 126 mapping(); 127 cout<<m-dinic()<<endl; 128 return 0; 129 }
