2.1. igraph_random_sample — Generates an increasing random sequence of integers.

2.1. `igraph_random_sample` — Generates an increasing random sequence of integers.

int igraph_random_sample(igraph_vector_t *res, igraph_integer_t l, igraph_integer_t h, 
			 igraph_integer_t length);

This function generates an incresing sequence of random integer numbers from a given interval. The algorithm is taken literally from Jeffrey Scott Vitter: 'An Efficient Algorithm for Sequential Random Sampling', ACM Transactions on Mathematical Software, 13/1, 58--67. This method can be used for generating numbers from a very large interval, it is primilarly created for randomly selecting some edges from the sometimes huge set of possible edges in a large graph.

Arguments:

`res`:	Pointer to an initialized vector, this will hold the result. It will be resized to the proper size.
`l`:	The lower limit of the generation interval (inclusive).
`h`:	The upper limit of the generation interval (inclusive).
`length`:	The number of random integers to generate.

Returns:

Error code.

Time complexity: according to the referenced paper, the expected running time is O(length).