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#ifndef RANDOM_WEIGHT_H
#define RANDOM_WEIGHT_H
/**
* Get a random weighted choice.
*
* Weights are assumed to be non-negative, but are allowed to be zero.
* @param choices The vector of choice-weight pairs to choose from.
*
* @return A pointer to the item in the chosen pair, or NULL if all
* weights are zero.
*/
template <typename T>
T* random_choose_weighted(vector<pair<T, int> >& choices)
{
int total = 0;
for (unsigned int i = 0; i < choices.size(); i++)
total += choices[i].second;
int r = random2(total);
int sum = 0;
for (unsigned int i = 0; i < choices.size(); i++)
{
sum += choices[i].second;
if (sum > r)
return &choices[i].first;
}
return NULL;
}
/**
* Get an index for a random weighted choice using a fixed vector of
* weights.
*
* Entries with a weight <= 0 are skipped.
* @param choices The fixed vector with weights for each item.
*
* @return A index corresponding to the selected item, or -1 if all
* weights were skipped.
*/
template <typename T, int SIZE>
int random_choose_weighted(FixedVector<T, SIZE>& choices)
{
int total = 0;
for (int i = 0; i < SIZE; ++i)
if (choices[i] > 0)
total += choices[i];
int r = random2(total);
int sum = 0;
for (int i = 0; i < SIZE; ++i)
{
if (choices[i] <= 0)
continue;
sum += choices[i];
if (sum > r)
return i;
}
return -1;
}
#endif
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