I read this on Quora. Hope you find it useful. There are things that a segment tree can do but a BIT cannot : A BIT essentially works with cumulative quantities. When the cumulative quantity for interval [i..j] is required, it is found as the difference between cumulative quantities for [1…j] and [1…i-1]. This works … Read more
Expanding on my comments. There’s a very important concept here that’s called information entropy. Out of full disclosure, I’m the current world record holder of the digits of Pi at 10 trillion digits (10^13). I have approximately 10,000 copies of everyone’s social security number. However that doesn’t mean I can just hack into everyone’s accounts … Read more
You could always just use Data.Sequence. Alternatively, a well-known implementation of a purely functional queue is to use two lists. One for enqueue and another for dequeue. Enqueue would simply cons with the enqueue list. Dequeue takes the head of the dequeue list. When the dequeue list is shorter than the enqueue list, refill it … Read more
I am sorry to disagree with the answer of Peter Walser. Solving the equations gives on my desk: u = ((bs.y – as.y) * bd.x – (bs.x – as.x) * bd.y) / (bd.x * ad.y – bd.y * ad.x) v = ((bs.y – as.y) * ad.x – (bs.x – as.x) * ad.y) / (bd.x * … Read more
An O(ND) Difference Algorithm and its Variations (1986, Eugene W. Myers) is a fantastic paper and you may want to start there. It includes pseudo-code and a nice visualization of the graph traversals involved in doing the diff. Section 4 of the paper introduces some refinements to the algorithm that make it very effective. Successfully … Read more
I learned that depth and height are properties of a node: The depth of a node is the number of edges from the node to the tree’s root node.A root node will have a depth of 0. The height of a node is the number of edges on the longest path from the node to … Read more
alt text http://imagebin.ca/img/yhFOHb.png Diagram After you find intersection of lines L1:Ax+By=C and L2:ax+by=c i.e. point A(x1,y1). Define two more lines y = ceil(y1) and y = floor(y1) parallel to X-axis and find their intersection with L1 and L2 i.e. Points B(x2,y2) and C(x3,y3). Then point you require is D or E whichever is closer to … Read more
With respect to data structures, Chris Okasaki has done substantial research into adopting classic data structures into a purely functional setting, as many of the standard data structures no longer work when using destructive updates. His book “Purely Functional Data Structures” shows how some structures, like binomial heaps and red/black trees, can be implemented quite … Read more
As you said some-word -> [doc385, doc211, doc39977, …] (sorted by rank, descending), I think the search engine may not do this, the doc list should be sorted by doc ID, each doc has a rank according to the word. When a query comes, it contains several keywords. For each word, you can find a … Read more
I believe the approach is to actually use a 3 dimensional noise field (every point in a 3D space has a scalar noise value) as opposed to a 2 dimensional field (every point on a 2D plane has a noise value). When using a 2D noise function to generate a height map, you offset the … Read more