How should I practice Largest Number After Removing K Digits?

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

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

Largest Number After Removing K Digits

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Problem statement

Given a decimal string num and an integer k, remove exactly k digits while preserving the relative order of the remaining digits.

Return the largest possible remaining integer as a string. Remove leading zeroes from the result. If no digit remains or the result contains only zeroes, return "0".

Function

largestAfterRemovingKDigits(num: String, k: int) → String

Examples

Example 1

num = "4902"k = 2return = "92"

Removing 4 and 0 leaves the largest order-preserving two-digit value.

Example 2

num = "1432219"k = 3return = "4329"

The greedy removals preserve the subsequence 4329.

Example 3

num = "10"k = 2return = "0"

Every digit is removed, so the canonical result is zero.

Constraints

1 <= num.length <= 200000.
num contains only decimal digits.
0 <= k <= num.length.