网络流一直没学,来学一波网络流. https://vjudge.net/problem/POJ-1273 题意:给定点数,边数,源点,汇点,每条边容量,求最大流. 解法:EK或dinic. EK:每次增广用bfs选择一条从源到汇具有最少边数的增广路径,然后找出该路径容量最小的边,就是此次增加的流量,然后沿该路径增加反向边,同时修改每条边的容量,重复上述过程直到找不到增广路(即minFlow = 0)为止. dinic: 每次bfs从源点到汇点分层(层数是源点到它最少要经过的边数),然后dfs从源…

题目链接: Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 67475   Accepted: 26075 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is cover…

Drainage Ditches Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 65146 Accepted: 25112 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by wate…

http://poj.org/problem?id=1273 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes quite a long time to regrow. Thus, Farmer Jo…

解题关键:最大流裸题 #include<cstdio> #include<cstring> #include<algorithm> #include<cstdlib> #include<cmath> #include<iostream> #include<queue> #include<vector> #define inf 0x3f3f3f3f #define MAX_V 252 using namespac…

Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 76000   Accepted: 29530 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by…

题目链接:poj1273 Drainage Ditches 呜呜,今天自学网络流,看了EK算法,学的晕晕的,留个简单模板题来作纪念... #include<cstdio> #include<vector> #include<queue> #include<cstring> #include<set> #include<algorithm> #define CLR(a,b) memset((a),(b),sizeof((a))) usi…

Drainage Ditches Time Limit: 1000MS Memory Limit: 10000K Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes quite a long time…

Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 68414   Accepted: 26487 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by…

题目链接:http://poj.org/problem?id=1273 Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes quite a long time to regrow. Thus, Farmer John has…

Drainage DitchesHal Burch Time Limit 1000 ms Memory Limit 65536 kb description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes quite a…

Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 78671   Accepted: 30687 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by…

描述 Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes quite a long time to regrow. Thus, Farmer John has built a set of drainage ditches s…

题目链接:http://poj.org/problem?id=1273 Time Limit: 1000MS Memory Limit: 10000K Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water for awhile and takes…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1532 Drainage Ditches Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 18864    Accepted Submission(s): 8980 Problem Description Every time it rain…

                                                                                        Drainage Ditches   Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by water f…

                                                         Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 69983   Accepted: 27151 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorit…

http://poj.org/problem?id=1273 Dinic算法 这是一道最大流的经典题 最大流尽量应该用边表,优于邻接矩阵(所以我写了邻接矩阵版的之后又写了个边表) 用了新学的Dinic算法 在每次找增广路之前先跑一遍bfs,把所有点的深度标记,按bfs记下的顺序找增广路,这条增广路上最小的边容量就是这条增广路的最大费用 跑出一条增广路之后,就开始更新现在的边剩余的容量,并建立反向边. #include<iostream> #include<cstdio> #incl…

这道题用dinic会超时 用E_K就没问题 注意输入数据有重边.POJ1273 dinic的复杂度为O(N*N*M)E_K的复杂度为O(N*M*M)对于这道题,复杂度是相同的. 然而dinic主要依靠Dfs寻找增广路,故而使用了太多次递归,而利用bfs寻找增广路(使用队列而不用递归)的EK等于用栈的方式实现了dinic的递归,所以 大幅提高了效率. 最大流算法的核心就是找到增广路并且增加反向边流量,理解了这个,最大流算法就很简单了. #include<iostream> #include<…

最大流的第一道题,刚开始学这玩意儿,感觉好难啊!哎····· 希望慢慢地能够理解一点吧! #include<stdio.h> #include<string.h> #include<queue> using namespace std; #define inf 1000000 #define min(a,b) a<b?a:b int map[210][210],pre[210],maxf[210]; int n,m; int bfs()//搜索,截止找不到增广路…

Description 给图,求最大流 最大流模板题,这里用dinic Code #include <cstdio> #include <cstring> #include <algorithm> #define Inf 0x7fffffff #define N 210 using namespace std; int g[N][N],d[N],q[N*10],h,t; int n,m,Ans,tmp; bool Bfs(){ memset(d,-1,sizeof(d)…

练一下最大流 #include <iostream> #include <cstring> #include <cstdio> #include <queue> using namespace std; int n, m, ron[205][205], pre[205], uu, vv, ww, vis[205]; queue<int> d; int ek(){ int maxFlow=0; while(1){ memset(vis, 0, si…

题目网址:http://acm.hdu.edu.cn/showproblem.php?pid=1532 思路: 网络流最大流的入门题,直接套模板即可~ 注意坑点是:有重边!!读数据的时候要用“+=”替换“=”. 对网络流不熟悉的,给一篇讲解:http://www.cnblogs.com/ZJUT-jiangnan/p/3632525.html. ✧(≖ ◡ ≖✿)我是看这篇博客才入门的. 代码: #include <cstdio> #include <cstring> #inclu…

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=1532 感觉题意不清楚,不知道是不是个人英语水平问题.本来还以为需要维护入度和出度来找源点和汇点呢,看讨论才知道1就是起点,m就是汇点..好想把代码写的工程化一点. #include <stdio.h> #include <string.h> #include <queue> #include <algorithm> using namespace std; c…

#include<cstdio> #include<algorithm> #include<cstring> #include<queue> #define N 250 #define M 250 #define INF 100000000 using namespace std; int head[N],cur[N],lev[N],ecnt=1,S,T,n,m; queue <int> q; struct adj { int nxt,v,w;…

#include<cstdio> #include<cstring> #include<algorithm> using namespace std; int n, m, S, T; ;//点数的最大值 ;//边数的最大值 const int INF = 0x3f3f3f3f; struct Edge { int to,next,cap,flow; } edge[MAXM]; //注意是MAXM int tol; int head[MAXN]; void init()…

#include <iostream> #include <queue> using namespace std; ][]; ]; //路径上每个节点的前驱节点 ]; int n,m; //m是顶点数目,顶点编号从1开始 1是源,m是汇, n是 边数 int Augment() { int v; int i; deque<int> q; memset(Prev,,sizeof(Prev)); memset(Visited,,sizeof(Visited)); Prev[…

题目背景 在农夫约翰的农场上,每逢下雨,贝茜最喜欢的三叶草地就积聚了一潭水.这意味着草地被水淹没了,并且小草要继续生长还要花相当长一段时间.因此,农夫约翰修建了一套排水系统来使贝茜的草地免除被大水淹没的烦恼(不用担心,雨水会流向附近的一条小溪).作为一名一流的技师,农夫约翰已经在每条排水沟的一端安上了控制器,这样他可以控制流入排水沟的水流量. 题目描述 农夫约翰知道每一条排水沟每分钟可以流过的水量,和排水系统的准确布局(起点为水潭而终点为小溪的一张网).需要注意的是,有些时候从一处到另一处不只有…

Drainage Ditches Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 67387   Accepted: 26035 Description Every time it rains on Farmer John's fields, a pond forms over Bessie's favorite clover patch. This means that the clover is covered by…

Drainage Ditches Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 16314    Accepted Submission(s): 7748 Problem Description Every time it rains on Farmer John's fields, a pond forms over Bessie'…