How should I practice Case-Insensitive Word Count?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Amazon phone screen problems in FastPrep.

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Case-Insensitive Word Count

Amazon● EasyFULLTIMEPHONE SCREEN

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Problem statement

Count the occurrences of each word in a text.

For this exercise, assume ASCII input. A word is a maximal consecutive run of English letters A-Z or a-z; every other character is a separator. Compare words case-insensitively and return lowercase words.

For this exercise, assume results follow the order of each word's first appearance. Represent each entry as word:count. Empty input or input with no words returns an empty list.

Function

wordFrequencies(text: String) → String[]

Examples

Example 1

text = "Hello world, HELLO!"return = ["hello:2","world:1"]

Matching ignores letter case; hello first appears before world.

Example 2

text = "red-blue red2green"return = ["red:2","blue:1","green:1"]

Hyphens and digits separate letter runs.

Example 3

text = ""return = []

There are no words.

Constraints

For this exercise, assume 0 <= text.length <= 10^4, with ASCII characters only.