網路流Ek演算法

標籤：queue   struct   rom   int   mem   詳細   span   max   for   

詳細解釋待.

紫書模板:

struct Edge {    int from, to, cap, flow;    Edge (int u, int v, int c, int f) : from(u), to(v), cap(c), flow(f) { }};struct EdmondsKarp {    int n, m;    vector<Edge> edges;    vector<int>  G[maxn];    int a[maxn];    int p[maxn];        void init(int n) {        for (int i=0; i<n; ++i) G[i].clear();        edges.clear();    }        void add(int u, int v , int val) {        edges.push_back(Edge(u, v, val, 0));        edges.push_back(Edge(u, v, 0, 0));        m = edges.size();        G[u].push_back(m-2);        G[v].push_back(m-1);    }        int Maxflow(int s, int t) {        int flow = 0;        while (1) {            memset(a, 0, sizeof(a));            queue<int> Q;            Q.push(s);            a[s] = inf;            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 (!a[e.to] && e.cap > e.flow) {                        p[e.to] = G[x][i];                        a[e.to] = min(a[x], e.cap - e.flow);                        Q.push(e.to);                    }                }                if (a[t]) break;            }            if (!a[t]) break;            for (int u = t; u!=s; u =edges[p[u]].from) {                edges[p[u]].flow += a[t];                edges[p[u]^1].flow -= a[t];            }            flow += a[t];        }        return flow;    }}Ek;

 

網路流Ek演算法