How do you compute the frequency of each number in a list?

To compute the frequency of each number in a list, iterate through the list and maintain a dictionary (or hash map) where the key is the number and the value is its count. For each element, increment its count in the dictionary. After the loop, the dictionary contains the frequency of every distinct number. In Python, you can also use collections.Counter, which automatically builds the frequency dictionary. The algorithm runs in O(n) time and uses O(k) additional space, where n is the list length and k is the number of unique elements.