Recursion and Big O Exercises

When the index is known, what is the time complexity for accessing an element in an array list?

What is the complexity of searching an ArrayList?

Given an array of ints, compute recursively the number of times that the value 11 appears in the array (no loops). We'll use the...

Given a non-negative int n, compute recursively (no loops) the count of the occurrences of 8 as a digit, except that an 8 with another 8...

Given a non-negative int n, return the sum of its digits recursively (no loops). Note that mod (%) by 10 yields the rightmost digit (126...

Given a string, compute recursively a new string where all the adjacent chars are now separated by a "*". So given "hello", return...

Given a string, compute the number of times lowercase "hi" appears in the string. Make the countHi be recursive.