hello everyone please someone explain me about the concept of virtual source in a graph containing negative cycle and how it can be used to find the vertices in the negative cycle in the graph using Bellman ford algorithm when the source vertex is not known. thanx.

Hello everyone..!! Yesterday i was trying to check the time taken by sorting techniques in this simple ques : http://www.codechef.com/problems/TSORT here the time limit is 5 sec and the no. of elements <=10^6 and the elements are <=10^6..as the optimal solution for this is hashing (or linear sorting) in O(n) i was trying to test for other sorting techniques too... and i observed following : 1. Heapsort : time limit exceeded 2. Mergesort : same 3. quicksort as expected same due to O(n^2) worst case 4.sort(a,a+n) in <algorithm.h> :same but the standard library function qsort passed now i can't understand that why qsort which is also qucicksort passed and mine other sorting techniques failed?? Is it that qsort works in different way or something else ... plzz help .. thanx :)