Meet your coaches
Talk through the problem while you code. Signed-in reps become prep memory for the next session.
Decode Ways
This problem is a state-machine in disguise, and DP is how you keep it under control. Interviewers love it because it reveals your state-and-transition thinking and your edge-case discipline. The trap is picking a state that's too vague; keep it minimal and consistent.
Learn this pattern
String Problems
String problems rely on frequency counting, two-pointer palindrome checks, and knowing when a trie helps. The difference between brute-force O(n²) and a clean O(n) solution is usually one of these three techniques.
Meet your coaches
Talk through the problem while you code. Signed-in reps become prep memory for the next session.
Chat with Fin or Coco right now on mobile.
Start talking through the problem here. Switch to desktop when you're ready to code and run tests.
Start coaching sessionStart a coached rep now. Sign in before or after the session so StrongYes can save what you struggled with to your prep memory.
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Desktop required
Sorry - mobile cannot run the editor and tests yet. Use the next step below or email yourself a link to continue on desktop.
String Problems gives you a useful next rep while you are still on your phone.