Tactic mode · Intuition builder
Don't memorize the answer. Build the instinct.
Play with one decision, code one line, assemble the pattern, run it, then adapt it to a new problem.
0XP
0%Mastery
0Stages
SL
Array / StringMedium
Sliding Window
Maintain a contiguous window boundary across arrays to reduce O(N²) to O(N)
Intuition coach
Grow a useful contiguous region, repair it only when it breaks, then measure it.
O(N) timeO(min(N, M)) space
Stage 1 · Play
Make one useful move
Start with the behavior of the pattern. The name and code can wait.
Mental animation
Longest Substring Without Repeating Characters
Grow a useful contiguous region, repair it only when it breaks, then measure it.
Keep true
The state describes exactly the elements between left and right.