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Palindromic Substrings
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. Once you define the right state, the transitions usually write themselves.
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.
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String Problems gives you a useful next rep while you are still on your phone.