Simulation

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 3813 note: count letters only, split into vowels and consonants; the score is 0 with no consonants, otherwise integer division

LeetCode 3679 note: the rule already decides what must be discarded, so simulate it; the length-w window counts only kept arrivals, and discarded ones must not be subtracted when they leave

LeetCode 3703 note: repeated replace is O(n^2); a stack of (character, run length) removes k ( plus k ) as soon as they line up

LeetCode 3701 note: add even indices and subtract odd ones; with slices, sum(nums[::2]) - sum(nums[1::2])

LeetCode 3688 note: OR only the even numbers; the starting value 0 is also the answer when there are none

Solving the Car Fleet problem using stack-based approach

LeetCode 1222 note: step outward from the king in eight directions; the first queen met in each direction can attack, with queens in a set for lookups

LeetCode 2402 note: one heap for free rooms and one for busy rooms; a delayed meeting keeps its original length

LeetCode 3612 note: simulate the four operations with a list; put the “result is non-empty” check inside the * branch, or * gets appended as a letter

LeetCode 1920 note: follow the definition ans[i] = nums[nums[i]]; for O(1) extra space, stack the new value times n on top of the old one