Dice game probabilities: Difference between revisions
Added C++ solution
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<pre>0.5731440767829801
0.6427886287176260</pre>
=={{header|C++}}==
<lang cpp>#include <cmath>
#include <cstdint>
#include <iomanip>
#include <iostream>
#include <map>
// Returns map from sum of faces to number of ways it can happen
std::map<uint32_t, uint32_t> get_totals(uint32_t dice, uint32_t faces) {
std::map<uint32_t, uint32_t> result;
for (uint32_t i = 1; i <= faces; ++i)
result.emplace(i, 1);
for (uint32_t d = 2; d <= dice; ++d) {
std::map<uint32_t, uint32_t> tmp;
for (const auto& p : result) {
for (uint32_t i = 1; i <= faces; ++i)
tmp[p.first + i] += p.second;
}
tmp.swap(result);
}
return result;
}
double probability(uint32_t dice1, uint32_t faces1, uint32_t dice2, uint32_t faces2) {
auto totals1 = get_totals(dice1, faces1);
auto totals2 = get_totals(dice2, faces2);
double wins = 0;
for (const auto& p1 : totals1) {
for (const auto& p2 : totals2) {
if (p2.first >= p1.first)
break;
wins += p1.second * p2.second;
}
}
double total = std::pow(faces1, dice1) * std::pow(faces2, dice2);
return wins/total;
}
int main() {
std::cout << std::setprecision(10);
std::cout << probability(9, 4, 6, 6) << '\n';
std::cout << probability(5, 10, 6, 7) << '\n';
return 0;
}</lang>
{{out}}
<pre>
0.5731440768
0.6427886287
</pre>
=={{header|D}}==
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