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Reactor Cooling
无源汇上下界最大流问题。
1、流量平衡。
2、满足上下界
模板题。
#include <iostream> #include <queue> #include <vector> #include <cstdio> #include <cstring> using namespace std; const int MAXN = 200000 + 10; const int INF = 1 << 30; struct Edge{ int from,to,cap,flow; Edge(){}; Edge(int _from,int _to,int _cap,int _flow) :from(_from),to(_to),cap(_cap),flow(_flow){}; }; vector<Edge> edges; vector<int> G[MAXN]; int d[MAXN],cur[MAXN]; int src,sink,N,M; bool vst[MAXN]; int b[MAXN],du[MAXN]; int sum; void init(){ src = N + 1; sink = src + 1; for(int i = 0;i <= sink;++i) G[i].clear(); edges.clear(); } void addEdge(int from,int to,int cap){ edges.push_back(Edge(from,to,cap,0)); edges.push_back(Edge(to,from,0,0)); int sz = edges.size(); G[from].push_back(sz - 2); G[to].push_back(sz - 1); } bool BFS(){ queue<int> Q; memset(vst,0,sizeof(vst)); Q.push(src); d[src] = 0; vst[src] = 1; while(!Q.empty()){ int x = Q.front(); Q.pop(); for(int i = 0;i < G[x].size();++i){ Edge& e = edges[G[x][i]]; if(!vst[e.to] && e.cap > e.flow){ vst[e.to] = 1; d[e.to] = d[x] + 1; Q.push(e.to); } } } return vst[sink]; } int DFS(int x,int a){ if(x == sink||a == 0) return a; int flow = 0,f; for(int& i = cur[x];i < G[x].size();++i){ Edge& e = edges[G[x][i]]; if(d[e.to] == d[x] + 1 && (f = DFS(e.to,min(a,e.cap - e.flow))) > 0){ e.flow += f; edges[G[x][i]^1].flow -= f; flow += f; a -= f; if(a == 0) break; } } return flow; } int maxFlow(){ int flow = 0; while(BFS()){ memset(cur,0,sizeof(cur)); flow += DFS(src,INF); } return flow; } void solve(){ int flow = maxFlow(); if(flow != sum){ puts("NO"); return; } puts("YES"); for(int i = 0;i < M;++i){ printf("%d\n",edges[i<<1].flow + b[i]); } } int main() { // freopen("Input.txt","r",stdin); int T; scanf("%d",&T); while(T--){ scanf("%d%d",&N,&M); init(); int u,v,c; memset(du,0,sizeof(du)); for(int i = 0;i < M;++i){ scanf("%d%d%d%d",&u,&v,&b[i],&c); addEdge(u,v,c - b[i]); du[u] -= b[i]; du[v] += b[i]; } sum = 0; for(int i = 1;i <= N;++i){ if(du[i] > 0){ addEdge(src,i,du[i]); sum += du[i]; } else addEdge(i,sink,-du[i]); } solve(); } return 0; }
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原文地址:http://www.cnblogs.com/lcchuguo/p/5053253.html