Easy

LeetCode 1464 note: all values are positive, so take the two largest a and b and return (a - 1)(b - 1)

LeetCode 1337 note: soldiers come first in each row, so binary search the first 0 for the count; sort by (count, row index) and take k

LeetCode 2331 note: leaves are 0 or 1 and internal nodes are 2 for OR and 3 for AND, evaluated in post-order

LeetCode 1379 note: walk both trees in lockstep; when the original reaches target, the clone’s node at the same position is the answer, comparing node identity

LeetCode 338 note: dp[i] = dp[i » 1] + (i & 1), or dp[i] = dp[i - highest power of two] + 1

LeetCode 1646 note: generate by the rules, nums[i // 2] at even i and nums[i // 2] + nums[i // 2 + 1] at odd i, handling n = 0 separately

LeetCode 1189 note: each letter supports count // needed balloons, with l and o needed twice; take the minimum

LeetCode 1184 note: a circular route has two directions; clockwise is the sum between start and destination, counterclockwise is the total minus that

LeetCode 1160 note: a word is formable when none of its character counts exceeds chars’; sum the lengths of such words

LeetCode 1137 note: like Fibonacci, roll three variables; watch the base values T0 = 0, T1 = T2 = 1 and the loop range

LeetCode 1128 note: normalize each domino to (small, large) as a key and count; a key with c dominoes yields c(c - 1) / 2 pairs

LeetCode 1122 note: count first, emit values in arr2’s order, then append the remaining values in ascending order