How should I practice Rearrange Digits Under an Adjacent-Sum Limit?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Amazon phone screen problems in FastPrep.

Is Rearrange Digits Under an Adjacent-Sum Limit associated with Amazon?

FastPrep tags this as a Amazon phone screen coding practice problem when the problem catalog has that company and stage context.

Rearrange Digits Under an Adjacent-Sum Limit

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Problem statement

You are given a non-empty string digits containing decimal digits. Rearrange every character exactly once so that the numeric values of every two adjacent digits have sum at most 9.

Return the lexicographically largest valid rearrangement. If no valid rearrangement exists, return the empty string.

Function

rearrangeDigits(digits: String) → String

Examples

Example 1

digits = "188"return = "818"

The only valid arrangement places 1 between the two 8s. Its adjacent sums are both 9.

Example 2

digits = "1234"return = "4321"

The descending arrangement is valid because its adjacent sums are 7, 5, and 3, and no valid result can be lexicographically larger.

Example 3

digits = "889"return = ""

Every pair among the three available digits has sum greater than 9, so no arrangement can use all of them.

Constraints

1 <= digits.length <= 100000
digits contains only characters '0' through '9'.
Leading zeroes are ordinary characters and must be preserved.