标签：des style blog color io os ar strong for
Description
Input
Output
Sample Input
Sample Output
#include <vector> #include <cstdio> #include <cstring> #include <queue> #define FOR(i,n) for(i=1;i<=(n);i++) using namespace std; const int INF = 2e9+10; const int N = 210; struct Edge{ int from,to,cap,flow; }; struct ISAP{ int n,m,s,t; int p[N],num[N]; vector<Edge> edges; vector<int> G[N]; bool vis[N]; int d[N],cur[N]; void init(int _n,int _m) { n=_n; m=_m; int i; edges.clear(); FOR(i,n) { G[i].clear(); d[i]=INF; } } void AddEdge(int from,int to,int cap) { edges.push_back((Edge){from,to,cap,0}); edges.push_back((Edge){to,from,0,0}); m = edges.size(); G[from].push_back(m-2); G[to].push_back(m-1); } bool BFS() { memset(vis,0,sizeof(vis)); queue<int> Q; Q.push(t); d[t]=0; vis[t]=1; while(!Q.empty()) { int x = Q.front(); Q.pop(); for(unsigned i=0;i<G[x].size();i++) { Edge& e = edges[G[x][i]^1]; if(!vis[e.from] && e.cap>e.flow) { vis[e.from]=1; d[e.from] = d[x]+1; Q.push(e.from); } } } return vis[s]; } int Augment() { int x=t, a=INF; while(x!=s) { Edge& e = edges[p[x]]; a = min(a,e.cap-e.flow); x = edges[p[x]].from; } x = t; while(x!=s) { edges[p[x]].flow+=a; edges[p[x]^1].flow-=a; x=edges[p[x]].from; } return a; } int Maxflow(int _s,int _t) { s=_s; t=_t; int flow = 0, i; BFS(); // FOR(i,n) printf("%d ",d[i]); puts(""); if(d[s]>=n) return 0; memset(num,0,sizeof(num)); memset(p,0,sizeof(p)); FOR(i,n) num[d[i]]++; int x=s; memset(cur,0,sizeof(cur)); while(d[s]<n) { if(x==t) { flow+=Augment(); x=s; } int ok=0; for(unsigned i=cur[x];i<G[x].size();i++) { Edge& e=edges[G[x][i]]; if(e.cap>e.flow && d[x]==d[e.to]+1) { ok=1; p[e.to]=G[x][i]; cur[x]=i; x=e.to; break; } } if(!ok) { int m=n-1; for(unsigned i=0;i<G[x].size();i++) { Edge& e=edges[G[x][i]]; if(e.cap>e.flow) m=min(m,d[e.to]); } if(--num[d[x]]==0) break; num[d[x]=m+1]++; cur[x]=0; if(x!=s) x=edges[p[x]].from; } } return flow; } }; ISAP isap; int main() { freopen("in","r",stdin); int n,m,u,v,c; while(scanf("%d%d",&m,&n)!=EOF) { isap.init(n,m); while(m--) { scanf("%d%d%d",&u,&v,&c); isap.AddEdge(u,v,c); //isap.AddEdge(v,u,c); } printf("%d\n",isap.Maxflow(1,n)); } return 0; }
ISAP 模板
注意用宏定义的FOR来做点的初始化，有些题目点所从0开始编号有些所从1开始，所以需要用一个宏定义
struct Edge{ int from,to,cap,flow; }; struct ISAP{ int n,m,s,t; int p[N],num[N]; vector<Edge> edges; vector<int> G[N]; bool vis[N]; int d[N],cur[N]; void init(int _n,int _m) { n=_n; m=_m; int i; edges.clear(); FOR(i,n) { G[i].clear(); d[i]=INF; } } void AddEdge(int from,int to,int cap) { edges.push_back((Edge){from,to,cap,0}); edges.push_back((Edge){to,from,0,0}); m = edges.size(); G[from].push_back(m-2); G[to].push_back(m-1); } bool BFS() { memset(vis,0,sizeof(vis)); queue<int> Q; Q.push(t); d[t]=0; vis[t]=1; while(!Q.empty()) { int x = Q.front(); Q.pop(); for(unsigned i=0;i<G[x].size();i++) { Edge& e = edges[G[x][i]^1]; if(!vis[e.from] && e.cap>e.flow) { vis[e.from]=1; d[e.from] = d[x]+1; Q.push(e.from); } } } return vis[s]; } int Augment() { int x=t, a=INF; while(x!=s) { Edge& e = edges[p[x]]; a = min(a,e.cap-e.flow); x = edges[p[x]].from; } x = t; while(x!=s) { edges[p[x]].flow+=a; edges[p[x]^1].flow-=a; x=edges[p[x]].from; } return a; } int Maxflow(int _s,int _t) { s=_s; t=_t; int flow = 0, i; BFS(); if(d[s]>=n) return 0; memset(num,0,sizeof(num)); memset(p,0,sizeof(p)); FOR(i,n) num[d[i]]++; int x=s; memset(cur,0,sizeof(cur)); while(d[s]<n) { if(x==t) { flow+=Augment(); x=s; } int ok=0; for(unsigned i=cur[x];i<G[x].size();i++) { Edge& e=edges[G[x][i]]; if(e.cap>e.flow && d[x]==d[e.to]+1) { ok=1; p[e.to]=G[x][i]; cur[x]=i; x=e.to; break; } } if(!ok) { int m=n-1; for(unsigned i=0;i<G[x].size();i++) { Edge& e=edges[G[x][i]]; if(e.cap>e.flow) m=min(m,d[e.to]); } if(--num[d[x]]==0) break; num[d[x]=m+1]++; cur[x]=0; if(x!=s) x=edges[p[x]].from; } } return flow; } };
HDU 1532 Drainage Ditches （网络流）
标签：des style blog color io os ar strong for
原文地址：http://www.cnblogs.com/someblue/p/3966903.html
