循环版,点的编号从0开始：
1 const int MAXN = 2010; 2 const int MAXM = 1200012; 3 const int INF = 0x3f3f3f3f; 4 struct Edge 5 { 6 int to, next, cap, flow; 7 }edge[MAXM]; 8 int tol; 9 int head[MAXN]; 10 void init() 11 { 12 tol = 2; 13 memset(head, -1, sizeof(head)); 14 } 15 void addedge(int u, int v, int w, int rw=0) 16 { 17 edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0; 18 edge[tol].next = head[u]; head[u] = tol++; 19 edge[tol].to = u; edge[tol].cap = rw; edge[tol].flow = 0; //存反向边 20 edge[tol].next = head[v]; head[v] = tol++; 21 } 22 int Q[MAXN]; 23 int dep[MAXN], cur[MAXN], sta[MAXN]; 24 bool bfs(int s, int t, int n) 25 { 26 int front = 0, tail = 0; 27 memset(dep, -1, sizeof(dep[0])*(n+1)); 28 dep[s] = 0; 29 Q[tail++] = s; 30 while(front < tail) 31 { 32 int u = Q[front++]; 33 for(int i = head[u]; i != -1; i = edge[i].next) 34 { 35 int v = edge[i].to; 36 if(edge[i].cap > edge[i].flow && dep[v] == -1)
{ 37 dep[v] = dep[u] + 1; 38 if(v == t) return true; 39 Q[tail++] = v; 40 } 41 } 42 } 43 return false; 44 } 45 int dinic(int s, int t, int n) { //s是源点编号，t是汇点编号，n是点的总数，返回最大流 46 int maxflow = 0; 47 while(bfs(s, t, n)) { 48 for(int i = 0; i < n; i++) cur[i] = head[i]; 49 int u = s, tail = 0; 50 while(cur[s] != -1) 51 { 52 if(u == t) 53 { 54 int tp = INF; 55 for(int i = tail-1; i >= 0; i--) 56 tp = min(tp, edge[sta[i]].cap-edge[sta[i]].flow); 57 maxflow+=tp; 58 for(int i = tail-1; i >= 0; i--) { 59 edge[sta[i]].flow+=tp; 60 edge[sta[i]^1].flow-=tp; 61 if(edge[sta[i]].cap-edge[sta[i]].flow==0) 62 tail = i; 63 } 64 u = edge[sta[tail]^1].to; 65 } 66 else 67 if(cur[u] != -1 && edge[cur[u]].cap > edge[cur[u]].flow && dep[u] + 1 == dep[edge[cur[u]].to]) 68 { 69 sta[tail++] = cur[u]; 70 u = edge[cur[u]].to; 71 } 72 else 73 { 74 while(u != s && cur[u] == -1) 75 u = edge[sta[--tail]^1].to; 76 cur[u] = edge[cur[u]].next; 77 } 78 } 79 } 80 return maxflow; 81 }
dfs增广路版，点的编号从0开始：
1 const int MAXN = 2010; 2 const int MAXM = 1200012; 3 const int INF = 0x3f3f3f3f; 4 struct Edge 5 { 6 int to, next, cap, flow; 7 }edge[MAXM]; 8 int tol; 9 int head[MAXN]; 10 void init() 11 { 12 tol = 2; 13 memset(head, -1, sizeof(head)); 14 } 15 void addedge(int u, int v, int w, int rw=0) 16 { 17 edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0; 18 edge[tol].next = head[u]; head[u] = tol++; 19 edge[tol].to = u; edge[tol].cap = rw; edge[tol].flow = 0; //存反向边 20 edge[tol].next = head[v]; head[v] = tol++; 21 } 22 int Q[MAXN]; 23 int dep[MAXN], cur[MAXN], sta[MAXN]; 24 bool bfs(int s, int t, int n) 25 { 26 int front = 0, tail = 0; 27 memset(dep, -1, sizeof(dep[0])*(n+1)); 28 dep[s] = 0; 29 Q[tail++] = s; 30 while(front < tail) 31 { 32 int u = Q[front++]; 33 for(int i = head[u]; i != -1; i = edge[i].next) 34 { 35 int v = edge[i].to; 36 if(edge[i].cap > edge[i].flow && dep[v] == -1) 37 { 38 dep[v] = dep[u] + 1; 39 if(v == t) return true; 40 Q[tail++] = v; 41 } 42 } 43 } 44 return false; 45 } 46 47 int dfs(int u,int t,int f) //dfs寻找增广路 48 { 49 if(u==t) return f; 50 for(int i=head[u];i!=-1;i=edge[i].next) 51 { 52 int v=edge[i].to; 53 if(edge[i].cap > edge[i].flow && dep[v]==dep[u]+1) 54 { 55 int d=dfs(v,t,min(f,edge[i].cap-edge[i].flow)); 56 if(d>0) 57 { 58 edge[i].flow+=d; 59 edge[i^1].flow-=d; 60 return d; 61 } 62 } 63 } 64 return 0; 65 } 66 67 int dinic(int s, int t, int n) { //s是源点编号，t是汇点编号，n是点的总数，返回最大流 68 int maxflow = 0 , f; 69 while(bfs(s, t, n)) 70 { 71 while(f=dfs(s,t,INF)) 72 maxflow+=f; 73 } 74 return maxflow; 75 }
不建反向边（一般用不到），点的编号从0开始：
1 const int MAXN = 100010; 2 const int MAXM = 1200012; 3 const int INF = 0x3f3f3f3f; 4 struct Edge 5 { 6 int from,to, next, cap, flow; 7 }edge[MAXM]; 8 int tol; 9 int head[MAXN]; 10 void init() 11 { 12 tol = 2; 13 memset(head, -1, sizeof(head)); 14 } 15 int min(int a,int b) 16 { 17 return a>b?b:a; 18 } 19 void addedge(int u, int v, int w, int rw=0) 20 { 21 edge[tol].from=u; //记录起点 22 edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0; 23 edge[tol].next = head[u]; head[u] = tol++; 24 } 25 int Q[MAXN]; 26 int dep[MAXN], cur[MAXN], sta[MAXN]; 27 bool bfs(int s, int t, int n) 28 { 29 int front = 0, tail = 0; 30 memset(dep, -1, sizeof(dep[0])*(n+1)); 31 dep[s] = 0; 32 Q[tail++] = s; 33 while(front < tail) 34 { 35 int u = Q[front++]; 36 for(int i = head[u]; i != -1; i = edge[i].next) 37 { 38 int v = edge[i].to; 39 if(edge[i].cap > edge[i].flow && dep[v] == -1) 40 { 41 dep[v] = dep[u] + 1; 42 if(v == t) return true; 43 Q[tail++] = v; 44 } 45 } 46 } 47 return false; 48 } 49 int dinic(int s, int t, int n) { //s是源点编号，t是汇点编号，n是点的总数，返回最大流 50 int maxflow = 0; 51 while(bfs(s, t, n)) { 52 for(int i = 0; i < n; i++) cur[i] = head[i]; 53 int u = s, tail = 0; 54 while(cur[s] != -1) 55 { 56 if(u == t) 57 { 58 int tp = INF; 59 for(int i = tail-1; i >= 0; i--) 60 tp = min(tp, edge[sta[i]].cap-edge[sta[i]].flow); 61 maxflow+=tp; 62 for(int i = tail-1; i >= 0; i--) { 63 edge[sta[i]].flow+=tp; 64 edge[sta[i]^1].flow-=tp; 65 if(edge[sta[i]].cap-edge[sta[i]].flow==0) 66 tail = i; 67 } 68 u = edge[sta[tail]].from; 69 } 70 else 71 if(cur[u] != -1 && edge[cur[u]].cap > edge[cur[u]].flow && dep[u] + 1 == dep[edge[cur[u]].to]) 72 { 73 sta[tail++] = cur[u]; 74 u = edge[cur[u]].to; 75 } 76 else 77 { 78 while(u != s && cur[u] == -1) 79 u = edge[sta[--tail]].from; 80 cur[u] = edge[cur[u]].next; 81 } 82 } 83 } 84 return maxflow; 85 }