Poj--1495（最大流）
2014-12-20 14:35:38
思路：经典的最大流，添加一个总源点和总汇点即可。
1 #include <cstdio> 2 #include <cstring> 3 #include <cstdlib> 4 #include <cmath> 5 #include <vector> 6 #include <map> 7 #include <set> 8 #include <stack> 9 #include <queue> 10 #include <iostream> 11 #include <algorithm> 12 using namespace std; 13 #define lp (p << 1) 14 #define rp (p << 1|1) 15 #define getmid(l,r) (l + (r - l) / 2) 16 #define MP(a,b) make_pair(a,b) 17 typedef long long ll; 18 typedef unsigned long long ull; 19 const int INF = 1 << 30; 20 const int maxn = 110; 21 22 int n,np,nc,m,c[maxn][maxn],lev[maxn]; 23 int Q[maxn],head,rear; 24 25 void Bfs(){ 26 memset(lev,-1,sizeof(lev)); 27 Q[head = rear = 1] = 0; 28 lev[0] = 0; 29 while(head <= rear){ 30 int x = Q[head++]; 31 for(int i = 1; i <= n + 2; ++i) if(lev[i] < 0 && c[x][i] > 0){ 32 lev[i] = lev[x] + 1; 33 Q[++rear] = i; 34 } 35 } 36 } 37 38 int Dfs(int p,int minf){ 39 if(p == n + 2) return minf; 40 for(int i = 1; i <= n + 2; ++i) if(lev[i] > lev[p] && c[p][i] > 0){ 41 int d = Dfs(i,min(c[p][i],minf)); 42 if(d > 0){ 43 c[p][i] -= d; 44 c[i][p] += d; 45 return d; //发现增广路 46 } 47 } 48 return 0; //无增广路 49 } 50 51 int Dinic(){ 52 int max_flow = 0,plus; 53 while(1){ 54 Bfs(); 55 if(lev[n + 2] < 0) break; 56 while((plus = Dfs(0,INF)) > 0) max_flow += plus; 57 } 58 return max_flow; 59 } 60 61 int main(){ 62 int t1,t2,t3; 63 while(scanf("%d%d%d%d",&n,&np,&nc,&m) != EOF){ 64 memset(c,0,sizeof(c)); 65 for(int i = 1; i <= m; ++i){ 66 scanf(" (%d,%d)%d",&t1,&t2,&t3); 67 c[++t1][++t2] += t3; 68 } 69 for(int i = 1; i <= np; ++i){ 70 scanf(" (%d)%d",&t1,&t2); 71 c[0][++t1] += t2; 72 } 73 for(int i = 1; i <= nc; ++i){ 74 scanf(" (%d)%d",&t1,&t2); 75 c[++t1][n + 2] += t2; 76 } 77 printf("%d\n",Dinic()); 78 } 79 return 0; 80 }
