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1949:Chores

题目描述
Farmer John's family pitches in with the chores during milking, doing all the chores as quickly as possible. At FJ's house, some chores cannot be started until others have been completed, e.g., it is impossible to wash the cows until they are in the stalls.

Farmer John has a list of N (3 <= N <= 10,000) chores that must be completed. Each chore requires an integer time (1 <= length of time <= 100) to complete and there may be other chores that must be completed before this chore is started. We will call these prerequisite chores. At least one chore has no prerequisite: the very first one, number 1. Farmer John's list of chores is nicely ordered, and chore K (K > 1) can have only chores 1,.K-1 as prerequisites. Write a program that reads a list of chores from 1 to N with associated times and all perquisite chores. Now calculate the shortest time it will take to complete all N chores. Of course, chores that do not depend on each other can be performed simultaneously.
输入解释
* Line 1: One integer, N

* Lines 2..N+1: N lines, each with several space-separated integers. Line 2 contains chore 1; line 3 contains chore 2, and so on. Each line contains the length of time to complete the chore, the number of the prerequisites, Pi, (0 <= Pi <= 100), and the Pi prerequisites (range 1..N, of course).
输出解释
A single line with an integer which is the least amount of time required to perform all the chores.
输入样例
7
5 0
1 1 1
3 1 2
6 1 1
1 2 2 4
8 2 2 4
4 3 3 5 6
输出样例
23
提示
[Here is one task schedule:

Chore 1 starts at time 0, ends at time 5.
Chore 2 starts at time 5, ends at time 6.
Chore 3 starts at time 6, ends at time 9.
Chore 4 starts at time 5, ends at time 11.
Chore 5 starts at time 11, ends at time 12.
Chore 6 starts at time 11, ends at time 19.
Chore 7 starts at time 19, ends at time 23.
]

该题目是Virtual Judge题目,来自 北京大学POJ

题目来源 USACO 2002 February

源链接: POJ-1949

最后修改于 2020-10-29T06:18:44+00:00 由爬虫自动更新

共提交 0

通过率 --%
时间上限 内存上限
3000 30000