问题 23831 --Remmarguts' Date(poj 2449)

23831: Remmarguts' Date(poj 2449)

时间限制: 1 Sec  内存限制: 128 MB
提交: 192  解决: 68
[提交][状态][讨论版][数据上传:][下载FPS1元][下载测试数据1元][512kb]

题目描述

"Good man never makes girls wait or breaks an appointment!" said the mandarin duck father. Softly touching his little ducks' head, he told them a story. 

"Prince Remmarguts lives in his kingdom UDF – United Delta of Freedom. One day their neighboring country sent them Princess Uyuw on a diplomatic mission." 

"Erenow, the princess sent Remmarguts a letter, informing him that she would come to the hall and hold commercial talks with UDF if and only if the prince go and meet her via the K-th shortest path. (in fact, Uyuw does not want to come at all)" 

Being interested in the trade development and such a lovely girl, Prince Remmarguts really became enamored. He needs you - the prime minister's help! 

DETAILS: UDF's capital consists of N stations. The hall is numbered S, while the station numbered T denotes prince' current place. M muddy directed sideways connect some of the stations. Remmarguts' path to welcome the princess might include the same station twice or more than twice, even it is the station with number S or T. Different paths with same length will be considered disparate. 


注意:中文和英文不是对等翻译,有英文水平好的可以翻译出来,下面的意思大体相同。注:英文不好可以理解但是把好好的英文翻成如此蹩脚的中文的确值得……

      A市有n个公交车站,某同学从第s个车站上车,从第t个车站下车,这n个车站中有m条单向路连接,由于某同学脑子有问题,他决定不走最短路而走第k短路(⊙﹏⊙),而且呢,他的路线中可以多次经过同一个站点(包括s和t),如果两点间有多条路径,即使路径长度相同,也视为不同路径。

输入

* 第1行: n,m(1 <= N <= 1000, 0 <= M <= 10000).车站的编号从1到n
* 第2到1+M行: 第i+1行表示第i条单向向道路,包含两个由空格隔开的整数: A_i和B_i以及它们之间的路径长度t(1<=t<=100)
*最后一行是s,t,k(1 <= S, T <= N, 1 <= K <= 1000)

输出

第k短路的长度,如果k短路不存在则输出“-1”(不含引号)

样例输入

2 2
1 2 5
2 1 4
1 2 2

样例输出

14

提示

来源

[提交][状态]