Going Home
1 //费用流初探 2 #include <iostream> 3 #include <queue> 4 #include <cstring> 5 #include <cstdio> 6 #include <algorithm> 7 using namespace std; 8 const int inf = 0x3f3f3f3f; 9 const int maxn = 110; 10 char gra[maxn][maxn]; 11 12 const int maxv = 210; 13 const int maxe = 210 * 210; 14 struct Edge{ 15 int u, v, cap, flow, cost; 16 int nxt; 17 Edge(int u = 0, int v = 0, int cap = 0, int flow = 0, int cost = 0, int nxt = 0) : u(u), v(v), cap(cap), flow(flow), cost(cost), nxt(nxt) {} 18 }e[maxe << 1]; 19 int head[maxv]; 20 int cnt = 0; 21 void init(){ 22 memset(head, -1, sizeof(head)); 23 cnt = 0; 24 } 25 void add(int u, int v, int cap, int flow, int cost){ 26 e[cnt] = Edge(u, v, cap, flow, cost, head[u]); 27 head[u] = cnt++; 28 e[cnt] = Edge(v, u, 0, flow, -cost, head[v]); 29 head[v] = cnt++; 30 } 31 int mx[maxv], my[maxv], hx[maxv], hy[maxv]; 32 33 int s, t, N; 34 int d[maxv], p[maxv], inq[maxv], a[maxv]; 35 bool BellmandFord(int s, int t, int &flow, int &cost){ 36 for(int i = 0; i < N; i++) d[i] = inf; 37 memset(inq, 0, sizeof inq); 38 d[s] = 0; inq[s] = 1; p[s] = 0; a[s] = inf; 39 queue<int> q; 40 q.push(s); 41 while(!q.empty()){ 42 int u = q.front(); q.pop(); 43 inq[u] = 0; 44 for(int i = head[u]; ~i; i = e[i].nxt){ 45 Edge &tp = e[i]; 46 if(tp.cap > tp.flow && d[tp.v] > d[u] + tp.cost){ 47 d[tp.v] = d[u] + tp.cost; 48 p[tp.v] = i; 49 a[tp.v] = min(a[u], tp.cap - tp.flow); 50 if(!inq[tp.v]) { 51 q.push(tp.v); 52 inq[tp.v] = 1; 53 } 54 } 55 } 56 } 57 if(d[t] == inf) return false; 58 flow += a[t]; 59 cost += d[t] * a[t]; 60 int u = t; 61 while(u != s){ 62 e[p[u]].flow += a[t]; 63 e[p[u] ^ 1].flow -= a[t]; 64 u = e[p[u]].u; 65 } 66 return true; 67 } 68 int MCMF(){ 69 int flow = 0, cost = 0; 70 while(BellmandFord(s, t, flow, cost)) ; 71 return cost; 72 } 73 74 int main(){ 75 //freopen("in.txt", "r", stdin); 76 //freopen("out.txt", "w", stdout); 77 int n, m; 78 while(scanf("%d %d", &n, &m) && (n || m)){ 79 int cth = 0, ctm = 0; 80 81 init(); 82 for(int i = 0; i < n; i++) { 83 scanf("%s", gra[i]); 84 for(int j = 0; j < m; j++){ 85 if(gra[i][j] == ‘H‘){ 86 hx[cth] = i; 87 hy[cth++] = j; 88 } 89 if(gra[i][j] == ‘m‘){ 90 mx[ctm] = i; 91 my[ctm++] = j; 92 } 93 } 94 } 95 for(int i = 0; i < cth; i++){ 96 for(int j = 0; j < ctm; j++){ 97 int dis = abs(hx[i] - mx[j]) + abs(hy[i] - my[j]); 98 add(i, cth + j, 1, 0, dis); 99 } 100 } 101 s = cth + ctm; 102 t = s + 1; 103 N = t + 1; 104 for(int i = 0; i < cth; i++){ 105 add(s, i, 1, 0, 0); 106 } 107 for(int i = 0; i < ctm; i++){ 108 add(cth + i, t, 1, 0, 0); 109 } 110 int ans = MCMF(); 111 printf("%d\n", ans); 112 } 113 return 0; 114 }
原文地址:https://www.cnblogs.com/yijiull/p/8318796.html
时间: 2024-11-06 12:44:35