105. find the first duplicate character in a string
JavaScriptApplestringShare
easy - accepted / - tried
Given a string which might have duplicate letters, write a function to find the first duplicate.
firstDuplicate('abca')
// 'a'
firstDuplicate('abcdefe')
// 'e'
firstDuplicate('abcdef')
// null
What is the time & space cost of your approach ? Can you do better?