0167EasyString

Trailing Tag Length

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Trains the technique from

This is an original problem, written from a brief that listed the technique, the difficulty, the topics, the function shape and the input bounds — none of that problem's wording, examples, hints or editorials. The link is there so you can map your practice onto the standard set.

Same function shape, different story and different numbers.

A dock scanner prints one line of routing text per pallet. The text is made only of English letters and blank spaces, and a run of letters with no blank inside it forms a single tag. Blanks are used purely as separators: the printer pads unpredictably, so a line can start with blanks, end with blanks, and carry several blanks between two neighbouring tags.

The rightmost tag on the line is the one the loader keys in, and the operator wants to know how many characters that tag occupies.

Report how many letters make up the final tag of line. Every line holds at least one tag, and padding blanks are never part of a tag.

Examples

Example 1

Input: line = "dock crew ready"
Output: 5

The final tag is `ready`, which occupies five characters.

Example 2

Input: line = " loading bay "
Output: 3

Padding sits at both ends of the print, and the rightmost tag is still `bay` with three letters.

Example 3

Input: line = "north pier"
Output: 4

Three blanks separate the two tags, and the one on the right, `pier`, has four letters.

Constraints

1 <= line.length <= 10^4
`line` contains English letters and the blank character ' ' only.
`line` holds at least one tag.

The signature

The editor is preloaded with this. It matches the parent problem's shape, so a solution that works here transfers to a judge unchanged.

Python

def trailing_tag_length(line: str) -> int:

Java

public int trailingTagLength(String line)

The intended approach

Time O(n)Space O(1)

Nothing to the left of the final tag matters, so work backwards from the last character. Skip the padding blanks first, then keep stepping left while letters keep appearing, counting as you go. The count stops at the blank that opens the final tag or at the start of the line, which needs no extra storage.

Pythonentry point: trailing_tag_length

def trailing_tag_length(line):
    # Time: O(n) -- in the worst case the scan touches every character once.
    # Space: O(1) -- only two integer cursors are kept.
    end = len(line) - 1
    while end >= 0 and line[end] == " ":
        end -= 1
    width = 0
    while end >= 0 and line[end] != " ":
        width += 1
        end -= 1
    return width

The obvious version

Cut the whole line apart on every blank, discard the empty pieces that padding creates, and measure the last piece that survives.

This is not filler. It was written independently of the fast solution and the two were run against thousands of random inputs to confirm they agree — which is how the answer above is known to be right. Read it when the intended approach feels like a rabbit pulled out of a hat.

Python

def bf_trailing_tag_length(line):
    tags = [chunk for chunk in line.split(" ") if chunk != ""]
    if not tags:
        return 0
    return len(tags[-1])

How this problem was checked

Reference solution executed against 12 test cases — 12 passed
3 worked examples confirmed by running the code
0 eight-word sequences shared with the parent problem's text
Agrees with an independent brute-force implementation on random inputs
Test set proven to catch deliberately broken solutions
Reviewed by a separate quality pass
Function arity matches the parent problem's

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