LeetCode

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

LeetCode 2859 note: count the set bits of the index, not of the value

LeetCode 154 note: compare with the right end as in LC 153; on equality the break could be on either side, so r -= 1, worst case O(n)

LeetCode 611 note: sort, fix the longest side k, and use two pointers for the shorter sides; when the sum is large enough every i in between works, adding j - i at once

LeetCode 540 note: before the single element every pair starts at an even index, so binary search whether nums[mid] equals nums[mid + 1] at an even mid

LeetCode 275 note: with sorted citations, find the first i where citations[i] >= n - i; the answer is n - i, in O(log n) with binary search

LeetCode 92 note: walk a dummy to the node before left, then move the following nodes one at a time to just after it, right - left times

LeetCode 1991 note: compute the total, maintain the left sum while scanning, and get the right sum as total - left - nums[i]

LeetCode 1732 note: the altitudes are prefix sums of gain starting from 0; take the maximum