Google·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

May 2026

Summary

Google SWE coding round, one problem the whole time. Seemed straightforward on the surface but the edge cases around duplicate letters made it messier than expected.

Questions Asked (1)

Given a list of letters that may contain duplicates, count the number of distinct ways to select and arrange letters from that list to spell the word 'GOOGLE'.

Algorithms & Data Structures

Author's notes

My first instinct was to just count frequencies and do some combinatorics math, but they pushed toward a backtracking solution.

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AI HintsAI Generated

Suggested Approach

Model the problem as counting the number of ways to choose positions for each required letter from the given multiset, then multiply by the number of distinct permutations of the chosen letters. Use combinatorics: for each letter, compute combinations of available occurrences, and then account for duplicate arrangements due to repeated letters in 'GOOGLE'.

Pro tip: Clarify whether the input list is a multiset (order doesn't matter) and whether the output should be modulo a large prime (common in Google interviews). Also, mention that if the list is large, precomputing factorials and inverse factorials modulo a prime enables O(1) combinations.

1. Clarify the problem

Confirm that the input is a list (multiset) of letters, that we need to count distinct arrangements of selected letters that form 'GOOGLE', and ask about constraints (size, modulo).

2. Count available letters

Build a frequency map of the given letters. Note that 'GOOGLE' requires: G:2, O:2, L:1, E:1.

3. Compute combinations for each letter

For each required letter, compute the number of ways to choose the needed count from the available frequency: C(avail, need). Multiply these together to get the number of ways to select the multiset of letters.

4. Account for permutations

The selected letters can be arranged in 6! / (2! * 2!) = 180 distinct ways because 'GOOGLE' has two G's and two O's. Multiply the selection count by 180 to get the total.

5. Handle edge cases and modulo

If any required letter is insufficient, return 0. If modulo is required, apply it after each multiplication and use modular inverse for combinations.

Key Points to Mention

Combinatorics: combinations (nCr) and permutations with duplicates
Frequency counting of input letters and target word
Multiplying independent choices for each letter
Handling insufficient letters (return 0)
Modular arithmetic for large numbers (if applicable)
Time complexity: O(n + k) where n is input size and k is distinct letters, or O(1) if using precomputed factorials

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