USACO 4.4 Pollutant Control
第一二问，可以通过*1001+1，最后ans/1001 ans%1001来解决，第三问，看题解后完全无想法，然后找了一种水过的办法，水过了。。这种做法应该是错的。
1 /* 2 ID:cuizhe 3 LANG: C++ 4 TASK: milk6 5 */ 6 #include <cstdio> 7 #include <cstring> 8 #include <cmath> 9 #include <queue> 10 using namespace std; 11 #define LL long long 12 LL INF; 13 LL flow[201][201]; 14 LL low[201]; 15 int path[201],used[201]; 16 int x[1001],y[1001]; 17 int str,end,n,m; 18 LL bfs() 19 { 20 int t,i; 21 memset(path,-1,sizeof(path)); 22 memset(used,0,sizeof(used)); 23 used[str] = 1; 24 queue<int> que; 25 que.push(str); 26 low[str] = INF; 27 while(!que.empty()) 28 { 29 t = que.front(); 30 que.pop(); 31 if(t == end) break; 32 for(i = 1; i <= n; i ++) 33 { 34 if(i != str&&!used[i]&&flow[t][i]) 35 { 36 low[i] = low[t] < flow[t][i] ? low[t]:flow[t][i]; 37 used[i] = 1; 38 path[i] = t; 39 que.push(i); 40 } 41 } 42 } 43 if(path[end] == -1) 44 return -1; 45 else 46 return low[end]; 47 } 48 LL EK() 49 { 50 LL res,now,ans = 0; 51 while((res = bfs()) != -1) 52 { 53 ans += res; 54 now = end; 55 while(now != str) 56 { 57 flow[now][path[now]] += res; 58 flow[path[now]][now] -= res; 59 now = path[now]; 60 } 61 } 62 return ans; 63 } 64 int main() 65 { 66 int i,sv,ev; 67 LL ans,w; 68 INF = (LL)9999999*9999999; 69 freopen("milk6.in","r",stdin); 70 freopen("milk6.out","w",stdout); 71 scanf("%d%d",&n,&m); 72 memset(flow,0,sizeof(flow)); 73 74 for(i = 1; i <= m; i ++) 75 { 76 scanf("%d%d%lld",&sv,&ev,&w); 77 x[i] = sv; 78 y[i] = ev; 79 flow[sv][ev] += ((LL)(w*1001+1)*500000 + i-1); 80 } 81 str = 1,end = n; 82 ans = EK(); 83 printf("%lld %lld\n",ans/500500000,(ans/500000)%1001); 84 for(i = 1;i <= m;i ++) 85 { 86 if(used[x[i]]&&!used[y[i]]) 87 printf("%d\n",i); 88 } 89 return 0; 90 }
