建立一个虚拟原点s和虚拟汇点t。s到每个H连接一个容量为1,花费为0的边。每个m到t连接一个容量为1,花费为0的边,然后每个H对每个m建边。
直接上板子。。
#include <stdio.h>
#include <string.h>
#include <vector>
#include <algorithm>
using namespace std;
struct edge
{
int to,cap,cost,rev;
edge(int _to = 0, int _cap = 0, int _cost = 0, int _rev = 0)
:to(_to),cap(_cap),cost(_cost),rev(_rev){}
};
const int INF = 0x3f3f3f3f;
const int MAX_V = 2222;
int V;
vector<edge> G[MAX_V];
int dist[MAX_V];
int prevv[MAX_V],preve[MAX_V];
void add_edge(int from, int to, int cap, int cost)
{
G[from].push_back(edge(to,cap,cost,G[to].size()));
G[to].push_back(edge(from,0,-cost,G[from].size()-1));
}
int min_cost_flow(int s, int t, int f)
{
int res = 0;
while(f > 0)
{
memset(dist,0x3f,sizeof(dist));
dist[s] = 0;
bool update = true;
while(update)
{
update = false;
for(int v = 0; v < V; ++v)
{
if(dist[v] == INF) continue;
for(int i = 0; i < G[v].size(); ++i)
{
edge& e = G[v][i];
if(e.cap > 0 && dist[e.to] > dist[v] + e.cost)
{
dist[e.to] = dist[v] + e.cost;
prevv[e.to] = v;
preve[e.to] = i;
update = true;
}
}
}
}
if(dist[t] == INF)
return -1;
int d = f;
for(int v = t; v != s; v = prevv[v])
d = min(d,G[prevv[v]][preve[v]].cap);
f -= d;
res += d*dist[t];
for(int v = t; v != s; v = prevv[v])
{
edge& e = G[prevv[v]][preve[v]];
e.cap -= d;
G[v][e.rev].cap += d;
}
}
return res;
}
struct node
{
char ch;
int x,y,id;
node(){}
node(char _ch, int _x, int _y, int _id)
:ch(_ch),x(_x),y(_y),id(_id){}
};
vector<node> ns;
int main()
{
int n,m,cnt,s,t,flow;
char ch;
while(scanf("%d %d",&n,&m) && n+m)
{
flow = 0;
ns.clear();
cnt = 0;
for(int i = 0; i < n; ++i)
{
getchar();
for(int j = 0; j < m; ++j)
{
ch = getchar();
if(ch == 'H') ++flow;
if(ch != '.') ns.push_back(node(ch,i,j,cnt++));
}
}
for(int i = 0; i <= cnt+2; ++i) G[i].clear();
V = cnt+2;
int len = ns.size();
s = len;
t = len+1;
for(int i = 0; i < len; ++i)
{
//向汇点连边
if(ns[i].ch == 'm')
add_edge(ns[i].id,t,1,0);
//和原点建边 并且扫出来每一个m
else
{
add_edge(s,ns[i].id,1,0);
for(int j = 0; j < len; ++j)
if(ns[j].ch == 'm')
add_edge(ns[i].id,ns[j].id,1,abs(ns[i].x-ns[j].x)+abs(ns[i].y-ns[j].y));
}
}
int res = min_cost_flow(s,t,flow);
printf("%d\n",res);
}
return 0;
}