【费用流】 HDU 1853 Cyclic Tour 费用流 完备匹配(裸题)
n个城市m条街道 要求完全匹配
#include <cstdio> #include <cstring> #include <cstdlib> #include <string> #include <iostream> #include <algorithm> #include <sstream> #include <cmath> using namespace std; #include <queue> #include <stack> #include <vector> #include <deque> #include <set> #include <map> #include <time.h>; #define cler(arr, val) memset(arr, val, sizeof(arr)) #define FOR(i,a,b) for(int i=a;i<=b;i++) #define IN freopen ("in.txt" , "r" , stdin); #define OUT freopen ("out.txt" , "w" , stdout); typedef long long LL; const int MAXN = 500; const int MAXM = 100000; const int INF = 0x3f3f3f3f; //const int INF = 922222; const int mod = 1000000007; struct Edge { int to,next,cap,flow,cost; } edge[MAXM]; int head[MAXN],tol; int pre[MAXN],dis[MAXN]; bool vis[MAXN]; void init() { tol=0; cler(head,-1); } void addedge(int u,int v,int cap,int cost) { edge[tol].to=v; edge[tol].cap=cap; edge[tol].cost=cost; edge[tol].flow=0; edge[tol].next=head[u]; head[u]=tol++; edge[tol].to=u; edge[tol].cap=0; edge[tol].cost=-cost; edge[tol].flow=0; edge[tol].next=head[v]; head[v]=tol++; } bool spfa(int s,int t,int n) { queue<int>q; for(int i=0; i<n; i++) { dis[i]=INF; vis[i]=false,pre[i]=-1; } dis[s]=0; vis[s]=true; q.push(s); while(!q.empty()) { int u=q.front(); q.pop(); vis[u]=false; for(int i=head[u]; ~i; i=edge[i].next) { int v=edge[i].to; if(edge[i].cap>edge[i].flow&&dis[v]>dis[u]+edge[i].cost) { dis[v]=dis[u]+edge[i].cost; pre[v]=i; if(!vis[v]) { vis[v]=true; q.push(v); } } } } if(pre[t]==-1) return false; else return true; } int mincostmaxflow(int s,int t,int n,int &cost) { int flow=0; cost=0; while(spfa(s,t,n)) { int Min = INF; for(int i=pre[t]; ~i; i=pre[edge[i^1].to]) { if(Min>edge[i].cap-edge[i].flow) Min=edge[i].cap-edge[i].flow; } for(int i=pre[t]; ~i; i=pre[edge[i^1].to]) { edge[i].flow+=Min; edge[i^1].flow-=Min; cost+=edge[i].cost*Min; } flow+=Min; } return flow; } int main() { #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); //freopen("out.txt", "w", stdout); #endif int n,m; while(scanf("%d%d",&n,&m)!=EOF) { init(); int u,v,d; for(int i=0; i<m; i++) { scanf("%d%d%d",&u,&v,&d); addedge(u,v+n,1,d); } for(int i=1; i<=n; i++) { addedge(0,i,1,0); addedge(i+n,2*n+1,1,0); } int cost; if(mincostmaxflow(0,2*n+1,2*n+2,cost)==n) printf("%d\n",cost); else puts("-1"); } return 0; }