Array

LeetCode 3507 note: n is tiny, so simulate; the right side of a slice assignment must be a list

LeetCode 3494 note: for each potion, push forward to get the last wizard’s finish time (everyone must be free), then subtract backward to get each wizard’s finish time

LeetCode 1431 note: compute the maximum once; a kid is True when their candies plus the extra reach >= the maximum, since a tie counts

LeetCode 3487 note: free deletion means picking distinct values; take every non-negative one, or only the maximum when all are negative

LeetCode 3131 note: every element gets the same x, so x is the difference of the two minimums (or of the sums divided by the length)

LeetCode 735 note: scan left to right with a stack; only a right-moving top meeting a left-moving asteroid collides, the smaller explodes and equal sizes both do

LeetCode 1814 note: rearrange the condition into nums[i] - rev(nums[i]) == nums[j] - rev(nums[j]), count pairs per value, and remember the modulus

LeetCode 3075 note: choose k children from the happiest, where the i-th choice loses i, floored at 0

LeetCode 3074 note: apples can be split freely, so take boxes from the largest capacity until the total fits every apple

LeetCode 3071 note: count each value on and off the Y, enumerate the Y value a and background value b (a != b), and take the fewest cells to change

LeetCode 3070 note: submatrices containing the top-left corner are exactly the 2D prefix sums P[i][j]; count those <= k

LeetCode 3069 note: simulate the rule: the first two go to separate arrays, then each element joins the array whose last element is larger