what about some bitmap+vector approach like this: obtain bounding box of point cloud area coverage Do this if it is not already known. It should be simple O(N) cycle through all points. create map[N][N] of the area It is a ‘bitmap’ of the area for easy data density computation. Just create projection from area(x,y) -> … Read more
Robert Floyd invented a sampling algorithm for just such situations. It’s generally superior to shuffling then grabbing the first x elements since it doesn’t require O(y) storage. As originally written it assumes values from 1..N, but it’s trivial to produce 0..N and/or use non-contiguous values by simply treating the values it produces as subscripts into … Read more
public static int[] merge(int[] a, int[] b) { int[] answer = new int[a.length + b.length]; int i = 0, j = 0, k = 0; while (i < a.length && j < b.length) answer[k++] = a[i] < b[j] ? a[i++] : b[j++]; while (i < a.length) answer[k++] = a[i++]; while (j < b.length) answer[k++] = … Read more
Loops may achieve a performance gain for your program. Recursion may achieve a performance gain for your programmer. Choose which is more important in your situation!
You can try this C++ code. I’ve used it with 32 and 64-bit integers. I’m sure I got this from SO. template <typename T> T modpow(T base, T exp, T modulus) { base %= modulus; T result = 1; while (exp > 0) { if (exp & 1) result = (result * base) % modulus; … Read more
Here is a one liner: all(l[i] <= l[i+1] for i in range(len(l) – 1)) If using Python 2, use xrange instead of range. For reverse=True, use >= instead of <=.
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
So far I have been able to implement the telegram authorization completely, but not in your requested language – PHP, I used vb.Net. However, I believe the same logic should apply. Creating a Telegram Authorization Key Telegram API is no walk in the park. Studying existing src code could be quite daunting (IMHO). Hence my … Read more
The basic idea of a segmented sieve is to choose the sieving primes less than the square root of n, choose a reasonably large segment size that nevertheless fits in memory, and then sieve each of the segments in turn, starting with the smallest. At the first segment, the smallest multiple of each sieving prime … Read more
I thought I might briefly mention my own polygon clipping and offsetting library – Clipper. While Clipper is primarily designed for polygon clipping operations, it does polygon offsetting too. The library is open source freeware written in Delphi, C++ and C#. It has a very unencumbered Boost license allowing it to be used in both … Read more