It’s about accumulation, not queue efficiency. Fastpass works because it makes the individual items in the queue more efficient in “consuming” something. It’s not so much a queue like a processor waiting for instructions to execute as it is people waiting in line for food. In the case of people at Disneyland, it allows them … Read more
Use the distinct extension function: val a = arrayOf(“a”, “a”, “b”, “c”, “c”) val b = a.distinct() // [“a”, “b”, “c”] There’s also distinctBy function that allows one to specify how to distinguish the items: val a = listOf(“a”, “b”, “ab”, “ba”, “abc”) val b = a.distinctBy { it.length } // [“a”, “ab”, “abc”] As … Read more
radians = degrees * (pi/180) degrees = radians * (180/pi) As for implementation, the main question is how precise you want to be about the value of pi. There is some related discussion here
Dijkstra derives an eloquent solution in “A Discipline of Programming”. He attributes the problem to Hamming. Here is my implementation of Dijkstra’s solution. int main() { const int n = 20; // Generate the first n numbers std::vector<int> v(n); v[0] = 1; int i2 = 0; // Index for 2 int i5 = 0; // … Read more
You can compute the LCM of more than two numbers by iteratively computing the LCM of two numbers, i.e. lcm(a,b,c) = lcm(a,lcm(b,c))
Here’s my solution (in Python): def spiral(X, Y): x = y = 0 dx = 0 dy = -1 for i in range(max(X, Y)**2): if (-X/2 < x <= X/2) and (-Y/2 < y <= Y/2): print (x, y) # DO STUFF… if x == y or (x < 0 and x == -y) or … Read more
Finally! Following up leads in sdcvvc’s answer, we have it: the O(n log n) algorithm for the problem! It is simple too, after you understand it. Those who guessed FFT were right. The problem: we are given a binary string S of length n, and we want to find three evenly spaced 1s in it. … Read more
First, compute the center point. Then sort the points using whatever sorting algorithm you like, but use special comparison routine to determine whether one point is less than the other. You can check whether one point (a) is to the left or to the right of the other (b) in relation to the center by … 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 currently study such problems — classification, nearest neighbor searching — for music information retrieval. You may be interested in Approximate Nearest Neighbor (ANN) algorithms. The idea is that you allow the algorithm to return sufficiently near neighbors (perhaps not the nearest neighbor); in doing so, you reduce complexity. You mentioned the kd-tree; that is … Read more