题意:有一个技能学习表,是一个DAG,要想正常学习到技能x,要将指向x的技能全部先学到,然后会有一个正常花费cx.然后你还有一种方案,通过氪金dx直接获得技能x.你还可以通过一定的代价,切断一条边.问你学得指定的技能N的最小代价. 源点向每个点连接代价为cx的边,每个点拆点,内部连接代价为dx的边,然后N向汇点连接代价为无穷的边,然后每条原图中的边的容量为切断其的代价. 容易发现,每一个割集的方案恰好对应一种学习到N的所需代价的方案.所以直接跑最小割即可. #include<cstdio> #…

Problem Description Elves are very peculiar creatures. As we all know, they can live for a very long time and their magical prowess are not something to be taken lightly. Also, they live on trees. However, there is something about them you may not kn…

http://acm.hdu.edu.cn/showproblem.php?pid=5441 Travel Time Limit: 1500/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 2061    Accepted Submission(s): 711 Problem Description Jack likes to travel around the wo…

http://acm.hdu.edu.cn/showproblem.php?pid=5444 Elven Postman Time Limit: 1500/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 939    Accepted Submission(s): 520 Problem Description Elves are very peculiar crea…

Elven Postman Time Limit: 1500/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 591    Accepted Submission(s): 329 Problem Description Elves are very peculiar creatures. As we all know, they can live for a very…

ACM ICPC Central Europe Regional Contest 2013 Jagiellonian University Kraków Problem A: Rubik’s RectangleProblem B: What does the fox say?Problem C: Magical GCDProblem D: SubwayProblem E: EscapeProblem F: DraughtsProblem G: History courseProblem H: C…

题目链接: Hdu 5442 Favorite Donut 题目描述: 给出一个文本串,找出顺时针或者逆时针循环旋转后,字典序最大的那个字符串,字典序最大的字符串如果有多个,就输出下标最小的那个,如果顺时针和逆时针的起始下标相同,则输出顺时针. 解题思路: 看到题目感觉后缀数组可以搞,正准备犯傻被队友拦下了,听队友解释一番,果断丢锅给队友.赛后试了一下后缀数组果然麻烦的不要不要的(QWQ),还是最大最小表示法 + KMP来的干净利索. 最大表示法:对于一个长度为len文本串,经过循环旋转得到长度…

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=5493 题目大意: N个人,每个人有一个唯一的高度h,还有一个排名r,表示它前面或后面比它高的人的个数,求按身高字典序最小同时满足排名的身高排列. 题目思路: [线段树] 首先可以知道,一个人前面或后面有r个人比他高,那么他是第r+1高或第n-i-r+1高,i为这个人是第几高的. 所以先将人按照身高从小到大排序,接下来,把当前这个人放在第k=min(r+1,n-i-r+1)高的位置. 用线段树维护包…

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=5492 题目大意: 一个N*M的矩阵,一个人从(1,1)走到(N,M),每次只能向下或向右走.求(N+M-1)ΣN+M-1(Ai-Aavg)2最小.Aavg为平均值. (N,M<=30,矩阵里的元素0<=C<=30) 题目思路: [动态规划] 首先化简式子,得原式=(N+M-1)ΣN+M-1(Ai2)-(ΣN+M-1Ai)2 f[i][j][k]表示走到A[i][j]格子上,此时前i+j-1…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=5458 Problem Description Given an undirected connected graph G with n nodes and m edges, with possibly repeated edges and/or loops. The stability of connectedness between node u and node v is defined by…