LeetCode 15 3Sum - Why Naive Fails

Check all triplets $(i, j, k)$ with three nested loops. Compute each sum, collect those equal to zero.

With $n = 3000$, you have roughly $\binom{3000}{3} \approx 4.5 \times 10^9$ triplets. That's far too slow.

Beyond speed, you'd generate duplicate triplets. For [-1, -1, 0, 1], the triplet [-1, 0, 1] appears twice using different -1 values.