IQ Lab: coding interviews from the first loop

easyLoops and basics target 15 min

To lower case

Not solved yetLeetCode 709. To Lower Case

Return a new string: s with each capital letter from A to Z changed to its lowercase partner (A to a, B to b, and so on). Every other character stays as it is: lowercase letters, digits, spaces and punctuation.

Change the letters yourself, one character at a time: do not call lower(), casefold() or swapcase(). Every character of s comes from ASCII, the basic table that gives each English letter, digit and common symbol a number from 0 to 127, called its code.

Example 1

Inputs = "Hash Map"Output"hash map"

Only H and M change.

Example 2

Inputs = "SQL99"Output"sql99"

Digits stay as they are.

Example 3

Inputs = "group by"Output"group by"

There is no capital to change, so the answer equals the input.

Constraints

0 ≤ len(s) ≤ 10⁵, so s can be empty.
Every character is printable ASCII: codes 32 (a space) to 126 (~).

Plan it first

Write a line for each before you code, then say them out loud. Compare with the Approach tab afterwards.

Walk In what order will you visit the input?Notebook What will you write down as you go?Promise What stays true after every step?Cost Time and space, in Big O.

Run examples checks the examples. Submit runs every test, including edge cases and, when the problem has one, a speed check on a large input.

Same pattern