Practice
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Index thinking, in-place tricks, prefix patterns — your current strength zone. We deepen it.
Trade space for time. Maps and sets turn O(n²) into O(n).
Two indices walking with a rule — sorted arrays and partitions.
Maintain a live window of interest. The gateway to string mastery.
Sorted world → log n. Lower/upper bound muscle memory.
LIFO + next greater patterns. Parentheses to daily temperatures.
Pointer surgery — reverse, merge, cycle detection.
Recursion on left/right. Depth, invert, sameness.
After arrays: stairs, robber, coins — think subproblems.
Classic HackerRank-style problems for yuvrajshukla1702 — each one taught slowly, then coded.