maxChar
Given a string, return the character that is most commonly used in the string.
Examples
maxChar('abcccccccd') → 'c'
maxChar('apple 1231111') → '1'
Starter code
function maxChar(str) {
}
Complexity of the optimal solution
Time O(n), space O(k). The function iterates through the string of length n once to build a character map, and then iterates through the map's keys (k). Since k <= n, the overall time complexity is O(n). The space for the map depends on the number of unique characters (k).