79 lines
2.5 KiB
MQL5
79 lines
2.5 KiB
MQL5
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//+------------------------------------------------------------------+
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//| PermutationGenerator.mqh |
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//| Copyright 2021, MetaQuotes Ltd. |
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//| https://www.mql5.com |
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//+------------------------------------------------------------------+
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#include "SimpleArray.mqh"
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//+------------------------------------------------------------------+
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//| Simple class for permutations generation |
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//+------------------------------------------------------------------+
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class PermutationGenerator
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{
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public:
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struct Result
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{
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int indices[]; // element indices in every position, e.g.
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}; // indices of chars from alphabet for every place in a string
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private:
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const int len; // number of positions in each set (set size)
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const int n; // number of different elements to choose for each position
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SimpleArray<Result> result; // here all variants are accumulated
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int indices[]; // array of element indices in current combination
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int gen(const int offset)
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{
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int depth = offset;
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// loop through positions in the set
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for(int i = offset; i < len; ++i)
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{
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// loop through candidate elements for every position
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for(int j = 0; j < n; ++j)
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{
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// place j-th element at i-th position
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indices[i] = j;
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if(i < len - 1)
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{
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// recursively do it for next positions
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depth = gen(i + 1);
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}
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else // i == len - 1, this is the last position
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{
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// got indices of next set of elements, the array is filled
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// ArrayPrint(indices); // debug
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Result r;
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ArrayCopy(r.indices, indices);
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result << r;
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}
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}
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// depth controls when job is done
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if(depth == len - 1)
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{
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break;
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}
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}
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return depth;
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}
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public:
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PermutationGenerator(const int length, const int elements) : len(length), n(elements) { }
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// main worker method
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SimpleArray<Result> *run()
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{
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// if a result exists already, return it right away
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if(result.size() > 0) return &result;
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ArrayResize(indices, len);
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gen(0);
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return &result;
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}
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};
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//+------------------------------------------------------------------+
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