DLUT 分食物

大意不在赘述。

思路：这是我有关图论的参考书上的一本书上的例题，我顺便把它写了一下。

具体的实现过程可以参考我的另一篇博客：http://blog.csdn.net/wall_f/article/details/8229629

#include <iostream>#include <cstdlib>#include <cstdio>#include <cstring>#include <string>using namespace std;const int MAXN = 10010;const int MAXM = 400010;const int INF = 0x3f3f3f3f;struct Edge{int v, f;int next;}edge[MAXM];int n, nf, nd;int cnt;int s, t;int first[MAXN], level[MAXN];int q[MAXN];char str[3000];void init(){cnt = 0;memset(first, -1, sizeof(first));}void read_graph(int u, int v, int f){edge[cnt].v = v, edge[cnt].f = f;edge[cnt].next = first[u], first[u] = cnt++;edge[cnt].v = u, edge[cnt].f = 0;edge[cnt].next = first[v], first[v] = cnt++;}int bfs(int s, int t){memset(level, 0, sizeof(level));level[s] = 1;int front = 0, rear = 1;q[front] = s;while(front < rear){int x = q[front++];if(x == t) return 1;for(int e = first[x]; e != -1; e = edge[e].next){int v = edge[e].v, f = edge[e].f;if(!level[v] && f){level[v] = level[x] + 1;q[rear++] = v;}}}return 0;}int dfs(int u, int maxf, int t){if(u == t) return maxf;int ret = 0;for(int e = first[u]; e != -1; e = edge[e].next){int v = edge[e].v, f = edge[e].f;if(level[v] == level[u] + 1 && f){int Min = min(maxf-ret, f);f = dfs(v, Min, t);edge[e].f -= f;edge[e^1].f += f;ret += f;if(ret == maxf) return ret;}}return ret;}int Dinic(int s, int t){int ans = 0;while(bfs(s, t)) ans += dfs(s, INF, t);return ans;}void read_case(){init();s = 0, t = nf+nd+n+n+1;for(int i = 1; i <= n; i++) //A,A1连一条边 {int A = nf+nd+i, A1 = nf+nd+n+i;read_graph(A, A1, 1);}for(int i = 1; i <= nf; i++) read_graph(s, i, 1); //源点与食物相连 for(int i = 1; i <= n; i++){int f2, d2;int A = nf+nd+i, A1 = nf+nd+n+i; //拆点为A,A1 scanf("%d%d", &f2, &d2);while(f2--){int v;scanf("%d", &v);read_graph(v, A, 1); //食物与A }while(d2--){int v;scanf("%d", &v);read_graph(A1, v+nf, 1); //A1与饮料 }}for(int i = 1; i <= nd; i++) read_graph(i+nf, t, 1); //汇点与饮料相连 }void solve(){read_case();int ans = Dinic(s, t);printf("%d\n", ans);}int main(){while(~scanf("%d%d%d", &n, &nf, &nd)){solve();}return 0;}