Misra-Gries heavy-hitters algorithm

Given the bag $b$ of $n$ elements and an integer $k \geq 2$. Find the values that occur more than $n/k$ times in $b$

idea: two passes over the values in $b$, while storing at most $k$ values from $b$ and their number of occurrences.

Assume the bag is available in array $b[0:n-1]$ of $n$ elements, then a heavy-hitter of bag $b$ is a value that occurs more than $n/k$ times in $b$ for some integer $k \geq 2$