probability of streak of K successes in N trials

#include <vector>
#include <cmath>

// this function adapted from
// http://www.askamathematician.com/2010/07/q-whats-the-chance-of-getting-a-run-of-k-successes-in-n-bernoulli-trials-why-use-approximations-when-the-exact-answer-is-known/
double probOfStreak(int numCoins, int minHeads, double headProb)
{
    std::vector<double> memo(numCoins+1);

    for (int i = 0; i < minHeads; ++i)
    {
        memo[i] = 0;
    }

    for (int i = minHeads; i <= numCoins; ++i)
    {
        double result = std::pow(headProb, minHeads);
        for (int firstTail = 1; firstTail <= minHeads; ++firstTail)
        {
            double pr = memo[i - firstTail];
            result += std::pow(headProb, firstTail-1) * (1 - headProb) * pr;
        }
        memo[i] = result;
    }

    return memo[numCoins];
}