连续最短路算法（Successive Shortest Path）（最小费用最大流）

 #include <cstdio>
 #include <cstring>
 #include <queue>
 #include <vector>
 #include <algorithm>
 using namespace std;
 #define N 205
 #define INF 0x3f3f3f3f
 struct node {
     int x, y;
     node () {}
     node (int x, int y) : x(x), y(y) {}
 };
 struct Edge {
     int cap, u, v, cost;
     Edge() {}
     Edge(int u, int v, int cap, int cost) : u(u), v(v), cap(cap), cost(cost) {}
 }edge[N*N];
 vector<node> p, h;
 vector<int> G[N];
 int tot, dis[N], inq[N], pre[N], S, T;

 void AddEdge(int u, int v, int cap, int cost) {
     edge[tot] = Edge(u, v, cap, cost);
     G[u].push_back(tot++);
     edge[tot] = Edge(v, u, , -cost);
     G[v].push_back(tot++);
 }

 int CalDis(int x1, int y1, int x2, int y2) {
     return abs(x1 - x2) + abs(y1 - y2);
 }

 bool SPFA() {
     memset(inq, , sizeof(inq));
     memset(dis, INF, sizeof(dis));
     queue<int> que; que.push(S);
     dis[S] = ; inq[S] = ;
     while(!que.empty()) {
         int u = que.front(); que.pop(); inq[u] = ;
         for(int i = ; i < G[u].size(); i++) {
             Edge &e = edge[G[u][i]];
             if(e.cap >  && dis[e.v] > e.cost + dis[u]) {
             // 当可以增广并且费用更小的时候
                 dis[e.v] = e.cost + dis[u];
                 pre[e.v] = G[u][i]; // 记录路径
                 if(inq[e.v]) continue;
                 que.push(e.v); inq[e.v] = ;
             }
         }
     }
     return dis[T] < INF;
 }

 void MFMC(int &mincost, int &maxflow) {
     int ans = , flow = INF, p;
     // 从汇点沿着此次增广的路径往回走,当找到源点的时候退出
     for(int u = T; u; u = edge[p].u) {
         p = pre[u]; // 找增广的流量
         if(edge[p].cap < flow) flow = edge[p].cap;
     }
     for(int u = T; u; u = edge[p].u) {
         p = pre[u];
         edge[p].cap -= flow; // 更新每条边的流量
         edge[p^].cap += flow;
         ans += flow * edge[p].cost; // 费用 = 单位费用 * 流量
     }
     mincost += ans, maxflow += flow;
 }

 int main() {
     int n, m;
     char s[];
     while(scanf("%d%d", &n, &m), n + m) {
         p.clear(); h.clear();
         for(int i = ; i < n; i++) {
             scanf("%s", s);
             for(int j = ; j < m; j++) {
                 if(s[j] == 'H') h.push_back(node(i, j));
                 if(s[j] == 'm') p.push_back(node(i, j));
             }
         }
         tot = ; int sz1 = p.size(), sz2 = h.size();
         S = , T = sz1 + sz2 + ;
         for(int i = ; i <= T; i++) G[i].clear();
         for(int i = ; i < sz1; i++) // S到man
             AddEdge(S, i + , , );
         for(int i = ; i < sz2; i++) // house到T
             AddEdge(i +  + sz1, T, , );
         for(int i = ; i < sz1; i++) {
             for(int j = ; j < sz2; j++) {
                 int c = CalDis(p[i].x, p[i].y, h[j].x, h[j].y);
                 AddEdge(i + , j +  + sz1, , c);
             }
         }

         int mincost = , maxflow = ;
         while(SPFA()) MFMC(mincost, maxflow);
         printf("%d\n", mincost);
     }
     return ;
 }