FrankE
e6329e1db4
deleting from the grid is now bleaching fast added new helper methods many new test-cases many new methods for geo classes and others added a bunch of new grid-walkers
90 lines
1.7 KiB
C++
90 lines
1.7 KiB
C++
#ifndef DRAWLIST_H
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#define DRAWLIST_H
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#include <vector>
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#include <random>
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#include <KLib/Assertions.h>
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/**
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* add elements of a certain probability
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* and randomly draw from them
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*/
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template <typename T> class DrawList {
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/** one entry */
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struct Entry {
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/** the user element */
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T element;
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/** the cumulative probability up to this element */
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double cumProbability;
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/** ctor */
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Entry(T element, const double cumProbability) : element(element), cumProbability(cumProbability) {;}
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/** compare for searches */
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bool operator < (const double val) const {return cumProbability < val;}
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};
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private:
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/** current cumulative probability */
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double cumProbability;
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/** all contained elements */
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std::vector<Entry> elements;
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/** random number generator */
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std::minstd_rand gen;
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public:
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/** ctor */
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DrawList() : cumProbability(0) {
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;
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}
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/** reset */
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void reset() {
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cumProbability = 0;
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elements.clear();
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}
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/** add a new user-element and its probability */
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void add(T element, const double probability) {
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cumProbability += probability;
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elements.push_back(Entry(element, cumProbability));
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}
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/** get a random element based on its probability */
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T get() {
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// generate random number between [0:cumProbability]
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std::uniform_real_distribution<> dist(0, cumProbability);
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// get a random value
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const double rndVal = dist(gen);
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// binary search for the matching entry O(log(n))
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const auto tmp = std::lower_bound(elements.begin(), elements.end(), rndVal);
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// sanity check
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_assertFalse(tmp == elements.end(), "draw() did not find a valid element");
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// done
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return (*tmp).element;
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}
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/** get the current, cumulative probability */
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double getCumProbability() const {
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return cumProbability;
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}
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};
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#endif // DRAWLIST_H
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