最短增广路算法
Dinic算法
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define INF 0x3f3f3f3f 4 #define M(a, b) memset(a, b, sizeof(a)) 5 const int N = 1e3 + 5; 6 struct Edge { 7 int from, to, cap, flow; 8 }; 9 10 struct Dinic { 11 int n, m, s, t; 12 vector<Edge> edges; 13 vector<int> G[N]; 14 bool vis[N]; 15 int d[N], cur[N]; 16 17 void AddEdge(int from, int to, int cap) { 18 edges.push_back((Edge){from, to, cap, 0}); 19 edges.push_back((Edge){to, from, 0, 0}); 20 m = edges.size(); 21 G[from].push_back(m-2); G[to].push_back(m-1); 22 } 23 24 bool bfs() { 25 M(vis, 0); 26 queue<int> q; 27 q.push(s); 28 d[s] = 0; vis[s] = 1; 29 while (!q.empty()) { 30 int x = q.front(); q.pop(); 31 for (int i = 0; i < G[x].size(); ++i) { 32 Edge &e = edges[G[x][i]]; 33 if (!vis[e.to] && e.cap > e.flow) { 34 vis[e.to] = 1; 35 d[e.to] = d[x] + 1; 36 q.push(e.to); 37 } 38 } 39 } 40 return vis[t]; 41 } 42 43 int dfs(int x, int a) { 44 if (x == t || a == 0) return a; 45 int flow = 0, f; 46 for (int &i = cur[x]; i < G[x].size(); ++i) { 47 Edge &e = edges[G[x][i]]; 48 if (d[e.to] == d[x] + 1 && (f = dfs(e.to, min(a, e.cap-e.flow))) > 0) { 49 e.flow += f; 50 edges[G[x][i]^1].flow -= f; 51 flow += f; a -= f; 52 if (a == 0) break; 53 } 54 } 55 return flow; 56 } 57 58 int Maxflow(int s, int t) { 59 this->s = s; this->t = t; 60 int flow = 0; 61 while (bfs()) { 62 M(cur, 0); 63 flow += dfs(s, INF); 64 } 65 return flow; 66 } 67 68 };
