Medium

LeetCode 633 note: converge a from 0 and b from isqrt(c); shrink b when the sum is too big and grow a when it is too small; watch for 0, a == b, and floating-point square roots

LeetCode 3820 note: three BFS runs give every node’s distance to the three targets

LeetCode 3819 note: pull out the non-negative values, rotate them left by k, and put them back into the non-negative positions in order; with none, do not take a modulo by 0

LeetCode 3818 note: find the longest strictly increasing suffix from the right; everything before it must go

LeetCode 2563 note: split “sum in [lower, upper]” into “sum <= upper” minus “sum <= lower - 1”, and count each with converging pointers over the sorted array in O(n)

LeetCode 1574 note: what remains is a non-decreasing prefix plus a non-decreasing suffix; find the longest of each, then join them with two pointers

LeetCode 1471 note: after sorting, the value farthest from the median is always at one of the ends, so converging pointers pick the stronger end k times

LeetCode 948 note: after sorting, buy score with the cheapest token and buy power with the most expensive one; trade for power only when score > 0, and stop when neither move works

LeetCode 923 note: sort, fix the first number, and find the other two with converging pointers; equal end values are counted with a combination, different ones by multiplying each end’s duplicate count

LeetCode 3775 note: count the first word’s vowels, then reverse every later word with the same count

LeetCode 2105 note: Alice from the left and Bob from the right, simulated with converging pointers; when they meet at the same plant, whoever has more water waters it

LeetCode 1877 note: after sorting, pair the smallest with the largest, the second smallest with the second largest, and take the largest pair sum with converging pointers