Maximum Product of Word Lengths

Problem

Given a string array words, return the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. If no such two words exist, return 0.

Examples

The brute-force approach

For every pair (i, j), check if they share any character. If not, compute the product and track the max.

best = 0
for i in range(n):
    for j in range(i+1, n):
        if not set(words[i]) & set(words[j]):
            best = max(best, len(words[i]) * len(words[j]))
return best

O(n² × L) — the intersection check costs O(L) per pair.

Spotting the pattern

This is a Bit Manipulation problem. The key question to ask yourself:

How does the bitwise AND of two word masks equal zero prove that the words share no letters?

Answering that is where it clicks, and it's exactly what the guided walkthrough below builds with you: the pattern reasoning, a progressive hint ladder that never spoils the answer, a row-by-row dry run, the optimized solution, and an in-browser editor to run your code against real test cases.