← Sliding Window

Micro-Drill #104 — Longest substring no repeats

Sliding Window Target: 15s

Hash-map window tracks last index of each char. Avoids set removal on duplicates.

seen = {}
l = res = 0
for r, c in enumerate(s):
    if c in seen and seen[c] >= l:
        l = seen[c] + 1
    seen[c] = r
    res = max(res, r - l + 1)

Type it from memory. Go.

Practice Problems

• 3. Longest Substring Without Repeating Characters
• 567. Permutation in String

Related Coding Drills

• Drill #102 — Longest Substring Without Repeating Characters Medium
• Drill #103 — Longest Repeating Character Replacement Medium