题目 Source http://acm.hdu.edu.cn/showproblem.php?pid=4807 Description The campus of Nanjing University of Science and Technology can be viewed as a graph with N vertexes and M directed edges (vertexes are numbered from 0 to N - 1). Each edge has the s…

Lunch Time http://acm.hdu.edu.cn/showproblem.php?pid=4807 Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 782    Accepted Submission(s): 183 Problem Description The campus of Nanjing University…

题意:      给你一个有向图,每条边上都有每一时刻的最大流量,有k个人在点0,他们要去点n-1,问你最晚到达的那个人最快要多久. 思路:      这个题目做了很多次,用过费用流,也用过最大流,结果都不行,怎么说的,这道题目用该是借助费用流的找新路径去枚举,可以说是费用流变形吧,首先我们一定要明白一点,就是时间的影响,单纯的最大流如果在时间的基础上考虑没什么意义,而费用流呢,我们想象一下,如果把时间设成费用那么我们就可以吧流量和时间结合起来了,在费用流的过程中我们要知道,他每一次都是根据最短…

题目链接: Coding Contest Time Limit: 2000/1000 MS (Java/Others)     Memory Limit: 65536/65536 K (Java/Others) Problem Description A coding contest will be held in this university, in a huge playground. The whole playground would be divided into N blocks,…

Coding Contest http://acm.hdu.edu.cn/showproblem.php?pid=5988 Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 5337    Accepted Submission(s): 1256 Problem Description A coding contest will be he…

Coding Contest Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 5968    Accepted Submission(s): 1413 Problem Description A coding contest will be held in this university, in a huge playground. Th…

题意: 思路: [问题分析] 求图的最大权不相交路径及其变种,用费用最大流解决. [建模方法] 规则(1) 把梯形中每个位置抽象为两个点<i.a>,<i.b>,建立附加源S汇T. 1.对于每个点i从<i.a>到<i.b>连接一条容量为1,费用为点i权值的有向边. 2.从S向梯形顶层每个<i.a>连一条容量为1,费用为0的有向边. 3.从梯形底层每个<i.b>向T连一条容量为1,费用为0的有向边. 4.对于每个点i和下面的两个点j,分别…

Going Home Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 22088   Accepted: 11155 Description On a grid map there are n little men and n houses. In each unit time, every little man can move one unit step, either horizontally, or vertica…

3130: [Sdoi2013]费用流 Time Limit: 10 Sec  Memory Limit: 128 MBSec  Special JudgeSubmit: 960  Solved: 505[Submit][Status][Discuss] Description Alice和Bob在图论课程上学习了最大流和最小费用最大流的相关知识.    最大流问题:给定一张有向图表示运输网络,一个源点S和一个汇点T,每条边都有最大流量.一个合法的网络流方案必须满足:(1)每条边的实际流量都不超…

思路: dp方法: 设dp[i][j][k][l]为两条没有交叉的路径分别走到(i,j)和(k,l)处最大价值. 则转移方程为 dp[i][j][k][l]=max(dp[i-1][j][k-1][l],dp[i][j-1][k-1][l],dp[i-1][j][k][l-1],dp[i][j-1][k][l-1])+map[i][j]+map[k][l]; 若两点相同减去一个map[i][j]即可 费用流方法(可以扩展为k条路径,但时间复杂度较高): 源点连接左上角点流量为k.费用为0,右下角…