hdu 1533 Going Home (最小费用最大流)

  1 #include <bits/stdc++.h>
  2 
  3 using namespace std;
  4 const int maxn = 200;
  5 const int N = 500020;
  6 const int M = 500020;
  7 const int inf = 0x3f3f3f3f;
  8 
  9 int n,m;
 10 struct Edge {
 11   int from, to, cap, flow;
 12   int  cost;
 13 };
 14 inline int Min(int aa,int bb)
 15 {
 16     return aa<bb?aa:bb;
 17 }
 18 vector < pair<int,int> > men;
 19 vector < pair<int,int> > house;
 20 struct MCMF {
 21     int n, m, s, t;
 22     vector<Edge> edges;
 23     vector<int> G[N];
 24     int inq[N];         // 是否在队列中
 25     int d[N];           // Bellman-Ford
 26     int p[N];           // 上一条弧
 27     int a[N];           // 可改进量
 28     void init(int n) {
 29         this->n = n;
 30         for(int i = 0; i < n; i++) G[i].clear();
 31         edges.clear();
 32     }
 33 
 34     void addedge(int from, int to, int cap, int cost) {
 35         edges.push_back((Edge){from, to, cap, 0, cost});
 36         edges.push_back((Edge){to, from, 0, 0, -cost});
 37         m = edges.size();
 38         G[from].push_back(m-2);
 39         G[to].push_back(m-1);
 40     }
 41     bool BellmanFord(int s, int t, int& flow,int& cost) {
 42         for(int i = 0; i < n; i++) d[i] = inf;
 43         memset(inq, 0, sizeof(inq));
 44         d[s] = 0; inq[s] = 1; p[s] = 0; a[s] = inf;
 45         queue<int> Q;
 46         Q.push(s);
 47         while(!Q.empty()) {
 48           int u = Q.front(); Q.pop();
 49           inq[u] = 0;
 50           int l=G[u].size();
 51           for(int i = 0; i < l; i++) {
 52             Edge& e = edges[G[u][i]];
 53             if(e.cap > e.flow && d[e.to] > d[u] + e.cost) {
 54               d[e.to] = d[u] + e.cost;
 55               p[e.to] = G[u][i];
 56               a[e.to] = Min(a[u], e.cap - e.flow);
 57               if(!inq[e.to]) { Q.push(e.to); inq[e.to] = 1; }
 58             }
 59           }
 60         }
 61         if(d[t] == inf) return false;
 62         cost += d[t]*a[t];
 63         int u = t;
 64         while(u != s) {
 65           edges[p[u]].flow += a[t];
 66           edges[p[u]^1].flow -= a[t];
 67           u = edges[p[u]].from;
 68         }
 69         return true;
 70     }
 71     int Mincost(int s, int t) {
 72         int cost = 0;
 73         int flow=0;
 74         while(BellmanFord(s, t,flow, cost));
 75         return cost;
 76     }
 77 }g;
 78 char s[maxn][maxn];
 79 int getid (int x,int y)
 80 {
 81     return (x-1)*m+y;
 82 }
 83 int x[maxn],xx[maxn];
 84 int y[maxn],yy[maxn];
 85 int nx,ny;
 86 int main() {
 87     //freopen("de.txt","r",stdin);
 88     while(~scanf("%d%d", &n, &m)) {
 89         if (n==0&&m==0)
 90             break;
 91         nx = ny = 0;
 92         g.init(n*m+100);
 93         int ffrom = n*m+ 1;int tto = n*m + 2;
 94         for(int i = 1; i <= n; ++i) {
 95             scanf("%s", s[i] + 1);
 96             for(int j = 1; j <= m; ++j) {
 97                 if(s[i][j] == ‘m‘) {
 98                     nx++;
 99                     x[nx] = i;
100                     y[nx] = j;
101                 }
102                 if(s[i][j] == ‘H‘) {
103                     ny++;
104                     xx[ny] = i;
105                     yy[ny] = j;
106                 }
107             }
108         }
109 
110         for(int i = 1; i <= nx; ++i) {
111             for(int j = 1; j <= ny; ++j) {
112                 int d = abs(x[i] - xx[j]);
113                 d += abs(y[i] - yy[j]);
114                 g.addedge(getid(x[i],y[i]), getid(xx[j],yy[j]), 1, d);
115             }
116         }
117         for(int i = 1; i <= nx; ++i) g.addedge(ffrom, getid(x[i],y[i]), 1, 0);
118         for(int i = 1; i <= ny; ++i) g.addedge(getid(xx[i],yy[i]), tto, 1, 0);
119         printf("%d\n", g.Mincost(ffrom, tto));
120     }
121     return 0;
122 }

  1 #include <bits/stdc++.h>
  2 
  3 using namespace std;
  4 const int maxn = 200;
  5 const int N = 500020;
  6 const int M = 500020;
  7 const int inf = 0x3f3f3f3f;
  8 
  9 int n,m;
 10 struct Edge {
 11   int from, to, cap, flow;
 12   int  cost;
 13 };
 14 inline int Min(int aa,int bb)
 15 {
 16     return aa<bb?aa:bb;
 17 }
 18 
 19 char s[maxn][maxn];
 20 
 21 struct zkw {
 22     int C, D;
 23     int s, t;
 24     int fst[N], nxt[M], vv[M], cap[M], flow[M], cost[M], e;
 25     bool vis[N];
 26     void init() {
 27         memset(fst, -1, sizeof fst);
 28         e = 0;
 29         C = D = 0;
 30     }
 31     void add(int u, int v, int f, int c) {
 32         vv[e] = v, nxt[e] = fst[u], cost[e] = c, cap[e] = f, flow[e] = 0, fst[u] = e++;
 33         vv[e] = u, nxt[e] = fst[v], cost[e] = -c, cap[e] = flow[e] = 0, fst[v] = e++;
 34     }
 35     int aug(int u, int f) {
 36         if(u == t) {
 37             C += D * f;
 38             return f;
 39         }
 40         vis[u] = 1;
 41         int tmp = f;
 42         for(int i = fst[u]; ~i; i = nxt[i]) {
 43             int v = vv[i];
 44             if(cap[i] > flow[i] && cost[i] == 0 && !vis[v]) {
 45                 int d = aug(v, tmp < cap[i] - flow[i]? tmp: cap[i] - flow[i]);
 46                 flow[i] += d;
 47                 flow[i^1] -= d;
 48                 tmp -= d;
 49                 if(!tmp) return f;
 50             }
 51         }
 52         return f - tmp;
 53     }
 54     bool modLabel() {
 55         int d = inf;
 56         for(int i = 0; i <= t; ++i) if(vis[i]) {
 57             for(int j = fst[i]; ~j; j = nxt[j]) {
 58                 int v = vv[j];
 59                 if(cap[j] > flow[j] && !vis[v] && cost[j] < d) d = cost[j];
 60             }
 61         }
 62         if(d == inf) return 0;
 63         for(int i = 0; i <= t; ++i) {
 64             if(vis[i]) {
 65                 for(int j = fst[i]; ~j; j = nxt[j]) {
 66                     int v = vv[j];
 67                     cost[j] -= d;
 68                     cost[j^1] += d;
 69                 }
 70             }
 71         }
 72         D += d;
 73         return 1;
 74     }
 75     int gao(int s, int t) {
 76         this -> s = s, this -> t = t;
 77         do do memset(vis, 0, sizeof vis);
 78         while(aug(s, inf)); while(modLabel());
 79         return C;
 80     }
 81 }g;
 82 
 83 int getid (int x,int y)
 84 {
 85     return (x-1)*m+y;
 86 }
 87 int x[maxn],xx[maxn];
 88 int y[maxn],yy[maxn];
 89 int nx,ny;
 90 int main() {
 91     //freopen("de.txt","r",stdin);
 92     while(~scanf("%d%d", &n, &m)) {
 93         if (n==0&&m==0)
 94             break;
 95         nx = ny = 0;
 96         g.init();
 97         int ffrom = n*m+ 1;int tto = n*m + 2;
 98         for(int i = 1; i <= n; ++i) {
 99             scanf("%s", s[i] + 1);
100             for(int j = 1; j <= m; ++j) {
101                 if(s[i][j] == ‘m‘) {
102                     nx++;
103                     x[nx] = i;
104                     y[nx] = j;
105                 }
106                 if(s[i][j] == ‘H‘) {
107                     ny++;
108                     xx[ny] = i;
109                     yy[ny] = j;
110                 }
111             }
112         }
113 
114         for(int i = 1; i <= nx; ++i) {
115             for(int j = 1; j <= ny; ++j) {
116                 int d = abs(x[i] - xx[j]);
117                 d += abs(y[i] - yy[j]);
118                 g.add(getid(x[i],y[i]), getid(xx[j],yy[j]), 1, d);
119             }
120         }
121         for(int i = 1; i <= nx; ++i) g.add(ffrom, getid(x[i],y[i]), 1, 0);
122         for(int i = 1; i <= ny; ++i) g.add(getid(xx[i],yy[i]), tto, 1, 0);
123         printf("%d\n", g.gao(ffrom, tto));
124     }
125     return 0;
126 }