Array

LeetCode 4041 note: with operations in any order, BFS finds every value a number can become (up to sum) with the fewest steps, then the same grouped 0/1 knapsack as 4040

LeetCode 4040 note: with multiplications before divisions, the best is always multiply-only or divide-only; list each number’s reachable values and costs, then run a grouped 0/1 knapsack

LeetCode 2585 note: a bounded (grouped) knapsack; each question type takes 0 to count questions, with capacity running backwards and the count enumerated inside

LeetCode 410 note: binary search the answer; for a cap mid, greedily fill each segment to count the fewest segments, and mid works if that count is <= k

LeetCode 3895 note: convert each number to a string and add up how many times the digit appears

LeetCode 1235 note: sort jobs by end time with best[j] = best profit using the first j jobs; taking job j binary-searches the last job ending <= its start

LeetCode 3873 note: merge points sharing an x or y into components; a new point joins at most two of them, so the answer is the two largest plus 1

LeetCode 2382 note: work backward so removals become additions; the Union-Find root stores the segment sum, and the maximum only grows

LeetCode 2355 note: ending at i, each shelf to the left takes one fewer book until a bottleneck shelf j with too few books; a monotonic stack finds j, and dp[i] = dp[j] + an arithmetic series

LeetCode 3989 note: the kept columns form a subsequence constrained only between neighbors; an LIS-style DP with dp[j] = the longest valid sequence ending at column j

LeetCode 1402 note: sort and take dishes from most satisfying down; each new dish goes first and shifts the chosen ones one slot later, adding the current chosen sum, so keep going while that sum is positive

LeetCode 1526 note: scanning left to right, every rise above the previous height needs that many new operations; drops reuse earlier operations