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104 lines
2.7 KiB
C++
104 lines
2.7 KiB
C++
/*
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* RNG.h, part of VCMI engine
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*
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* Authors: listed in file AUTHORS in main folder
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*
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* License: GNU General Public License v2.0 or later
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* Full text of license available in license.txt file, in main folder
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*
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*/
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#pragma once
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VCMI_LIB_NAMESPACE_BEGIN
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namespace vstd
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{
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class DLL_LINKAGE RNG
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{
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public:
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virtual ~RNG() = default;
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/// Returns random number in range [lower, upper]
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virtual int nextInt(int lower, int upper) = 0;
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/// Returns random number in range [lower, upper]
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virtual int64_t nextInt64(int64_t lower, int64_t upper) = 0;
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/// Returns random number in range [lower, upper]
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virtual double nextDouble(double lower, double upper) = 0;
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/// Returns random number in range [0, upper]
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virtual int nextInt(int upper) = 0;
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/// Returns random number in range [0, upper]
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virtual int64_t nextInt64(int64_t upper) = 0;
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/// Returns random number in range [0, upper]
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virtual double nextDouble(double upper) = 0;
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/// Generates an integer between 0 and the maximum value it can hold.
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/// Should be only used for seeding other generators
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virtual int nextInt() = 0;
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/// Returns integer using binomial distribution
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/// returned value is number of successfull coin flips with chance 'coinChance' out of 'coinsCount' attempts
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virtual int nextBinomialInt(int coinsCount, double coinChance) = 0;
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};
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}
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namespace RandomGeneratorUtil
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{
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template<typename Container>
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auto nextItem(const Container & container, vstd::RNG & rand) -> decltype(std::begin(container))
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{
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if(container.empty())
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throw std::runtime_error("Unable to select random item from empty container!");
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return std::next(container.begin(), rand.nextInt64(0, container.size() - 1));
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}
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template<typename Container>
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auto nextItem(Container & container, vstd::RNG & rand) -> decltype(std::begin(container))
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{
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if(container.empty())
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throw std::runtime_error("Unable to select random item from empty container!");
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return std::next(container.begin(), rand.nextInt64(0, container.size() - 1));
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}
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template<typename Container>
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size_t nextItemWeighted(Container & container, vstd::RNG & rand)
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{
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assert(!container.empty());
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int64_t totalWeight = std::accumulate(container.begin(), container.end(), 0);
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assert(totalWeight > 0);
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int64_t roll = rand.nextInt64(0, totalWeight - 1);
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for (size_t i = 0; i < container.size(); ++i)
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{
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roll -= container[i];
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if(roll < 0)
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return i;
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}
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return container.size() - 1;
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}
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template<typename T>
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void randomShuffle(std::vector<T> & container, vstd::RNG & rand)
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{
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int64_t n = (container.end() - container.begin());
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for(int64_t i = n-1; i>0; --i)
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{
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std::swap(container.begin()[i],container.begin()[rand.nextInt64(0, i)]);
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}
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}
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}
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VCMI_LIB_NAMESPACE_END
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