Frequency Counting Applications

Frequency counting solves many problems:

$1.$ Find the majority element (appears more than $n/2$ times)

$2.$ Check if two strings are anagrams (same character frequencies)

$3.$ Find elements appearing exactly $k$ times

$4.$ Count distinct elements

$5.$ Find the mode (most frequent element)

Whenever you see "count," "frequency," or "how many times," think hash map.