知识点:https://blog.csdn.net/x_y_q_/article/details/51999466
https://www.cnblogs.com/ZJUT-jiangnan/p/3632525.html
题集:https://blog.csdn.net/shahdza/article/details/7779537
1532.最大流
语法:https://blog.csdn.net/xiaofei0859/article/details/78452510
EK算法
1 #include <iostream> 2 #include <queue> 3 #include<string.h> 4 using namespace std; 5 #define arraysize 201 6 int maxData = 0x7fffffff; 7 int capacity[arraysize][arraysize]; //记录残留网络的容量 8 int flow[arraysize]; //标记从源点到当前节点实际还剩多少流量可用 9 int pre[arraysize]; //标记在这条路径上当前节点的前驱,同时标记该节点是否在队列中 10 int n,m;//m是汇点,n是边数 11 queue<int> myqueue; 12 int BFS(int src,int des) 13 { 14 int i,j; 15 while(!myqueue.empty()) //队列清空 16 myqueue.pop(); 17 for(i=1;i<m+1;++i) 18 { 19 pre[i]=-1; 20 } 21 pre[src]=0; 22 flow[src]= maxData; 23 myqueue.push(src); 24 while(!myqueue.empty()) 25 { 26 int index = myqueue.front(); 27 myqueue.pop(); 28 if(index == des) //找到了增广路径 29 break; 30 for(i=1;i<m+1;++i) 31 { 32 if(i!=src && capacity[index][i]>0 && pre[i]==-1) 33 { 34 pre[i] = index; //记录前驱 35 flow[i] = min(capacity[index][i],flow[index]); //关键:迭代的找到增量 36 myqueue.push(i); 37 } 38 } 39 } 40 if(pre[des]==-1) //残留图中不再存在增广路径 41 return -1; 42 else 43 return flow[des];//该流大小 44 } 45 int maxFlow(int src,int des) 46 { 47 int increasement= 0; 48 int sumflow = 0; 49 while((increasement=BFS(src,des))!=-1) 50 { 51 int k = des; //利用前驱寻找路径 52 while(k!=src) 53 { 54 int last = pre[k]; 55 capacity[last][k] -= increasement; //改变正向边的容量 56 capacity[k][last] += increasement; //改变反向边的容量 57 k = last; 58 } 59 sumflow += increasement; 60 } 61 return sumflow; 62 } 63 int main() 64 { 65 int i,j; 66 int start,end,ci; 67 while(cin>>n>>m) 68 { 69 memset(capacity,0,sizeof(capacity)); 70 memset(flow,0,sizeof(flow)); 71 for(i=0;i<n;++i) 72 { 73 cin>>start>>end>>ci; 74 if(start == end) //考虑起点终点相同的情况 75 continue; 76 capacity[start][end] +=ci; //此处注意可能出现多条同一起点终点的情况 77 } 78 cout<<maxFlow(1,m)<<endl; 79 } 80 return 0; 81 }
Dinic算法
知识点:http://www.cnblogs.com/SYCstudio/p/7260613.html
https://www.cnblogs.com/LUO77/p/6115057.html
https://www.cnblogs.com/y-clever/p/6308820.html
https://blog.csdn.net/baidu_35009437/article/details/52068468
https://comzyh.com/blog/archives/568/
1 #include <cstdio> 2 #include <string.h> 3 #include <queue> 4 using namespace std; 5 int const inf = 0x3f3f3f3f; 6 int const MAX = 205; 7 int n, m;//m是汇点,n是边数 8 int c[MAX][MAX], dep[MAX];//dep[MAX]代表当前层数 9 10 int bfs(int s, int t)//重新建图,按层次建图 11 { 12 queue<int> q; 13 while(!q.empty()) 14 q.pop(); 15 memset(dep, -1, sizeof(dep)); 16 dep[s] = 0; 17 q.push(s); 18 while(!q.empty()){ 19 int u = q.front(); 20 q.pop(); 21 for(int v = 1; v <= m; v++){ 22 if(c[u][v] > 0 && dep[v] == -1){//如果可以到达且还没有访问,可以到达的条件是剩余容量大于0,没有访问的条件是当前层数还未知 23 dep[v] = dep[u] + 1; 24 q.push(v); 25 } 26 } 27 } 28 return dep[t] != -1;//如等于-1则为无法分层的图 29 } 30 31 int dfs(int u, int mi, int t)//查找路径上的最小流量 32 { 33 if(u == t) 34 return mi; 35 int tmp; 36 for(int v = 1; v <= m; v++){ 37 if(c[u][v] > 0 && dep[v] == dep[u] + 1 && (tmp = dfs(v, min(mi, c[u][v]), t))){ 38 c[u][v] -= tmp; 39 c[v][u] += tmp; 40 return tmp; 41 } 42 } 43 return 0; 44 } 45 46 int dinic() 47 { 48 int ans = 0, tmp; 49 while(bfs(1, m)){ 50 while(1){ 51 tmp = dfs(1, inf, m); 52 if(tmp == 0) 53 break; 54 ans += tmp; 55 } 56 } 57 return ans; 58 } 59 60 int main() 61 { 62 while(~scanf("%d %d", &n, &m)){ 63 memset(c, 0, sizeof(c)); 64 int u, v, w; 65 while(n--){ 66 scanf("%d %d %d", &u, &v, &w); 67 c[u][v] += w; 68 } 69 printf("%d ", dinic()); 70 } 71 return 0; 72 }