Milking Time (poj 3616 简单DP)

Language: Default Milking Time Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 5290   Accepted: 2183 Description Bessie is such a hard-working cow. In fact, she is so focused on maximizing her productivity that she decides to schedule her next N (1 ≤ N ≤ 1,000,000) hours (conveniently labeled 0..N-1) so that she produces as much milk as possible. Farmer John has a list of M (1 ≤ M ≤ 1,000) possibly overlapping intervals in which he is available for milking. Each interval i has a starting hour (0 ≤ starting_houri ≤ N), an ending hour (starting_houri <ending_houri ≤ N), and a corresponding efficiency (1 ≤ efficiencyi ≤ 1,000,000) which indicates how many gallons of milk that he can get out of Bessie in that interval. Farmer John starts and stops milking at the beginning of the starting hour and ending hour, respectively. When being milked, Bessie must be milked through an entire interval. Even Bessie has her limitations, though. After being milked during any interval, she must rest R (1 ≤ R ≤ N) hours before she can start milking again. Given Farmer Johns list of intervals, determine the maximum amount of milk that Bessie can produce in the N hours. Input * Line 1: Three space-separated integers: N, M, and R * Lines 2..M+1: Line i+1 describes FJ's ith milking interval withthree space-separated integers: starting_houri , ending_houri , and efficiencyi Output * Line 1: The maximum number of gallons of milk that Bessie can product in the N hours Sample Input 12 4 2 1 2 8 10 12 19 3 6 24 7 10 31 Sample Output 43 Source USACO 2007 November Silver

题意：给个时间长度n，m个工作时间段和每个时间段能完成的工作量，一次只能做一个工作并且一旦开始做就要把它做完，要求选择的两个工作时间段之间至少相差r时间（中间需要休息嘛）求选择那些工作n时间内能完成的最大工作量。输出最大值。

思路：先按工作的结束时间从小到大排序，再动态规划。dp[i]表示从头开始取到第i段所获得的最大值。二重循环，如果第i段之前的某个段的结束时间加上r小于等于第i段的开始时间，则更新dp[i]。

代码：

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