1582 articles
LeetCode 1802 maximizes the value at a given index given a sum cap and adjacent-difference constraint. A textbook O(log maxSum) binary-search-on-answer with arithmetic series math.
LC 1060 asks for the kth missing number in a sorted array. Binary search on the missing-count function: at index i, exactly nums[i] - nums[0] - i numbers are missing. Find the first index where this count >= k, then recover the answer. O(log n).
Search a row-and-column sorted 2D matrix in O(m+n) using the staircase technique from the top-right corner. Understand why binary search alone fails and why the corner is the unique elimination point.
Place C cows in N stalls to maximise the minimum distance between any two cows. Learn the canonical binary-search-on-answer pattern — the template behind Magnetic Force Between Two Balls, Split Array, and dozens of other hard problems.
Count subarrays whose sum lies in [lower, upper] using merge sort on prefix sums in O(n log n). Understand the divide-and-conquer counting trick that makes an O(n^2) brute-force drop to linearithmic time.