LeetCode

LeetCode 1446 note: track the current run of equal characters in one pass, resetting to 1 on a change

LeetCode 412 note: check multiples of 15 first, then 5 and 3; multiples need %, not //

LeetCode 409 note: use an even number of each character on the two sides, plus one in the middle if any count is odd

LeetCode 405 note: add 2^32 to a negative number to get its two’s complement, then take 4 bits at a time (% 16); handle 0 separately

LeetCode 404 note: tell each child during DFS whether it is a left child, adding only left children that are leaves

LeetCode 392 note: two pointers; the pointer on t always advances, and the one on s advances on a match; bound-check both

LeetCode 389 note: t has one extra character; XOR every character of both strings, pairs cancel, and the extra one remains

LeetCode 387 note: count first, then scan left to right for the first character with count 1

LeetCode 383 note: every character’s demand in ransomNote must not exceed its supply in magazine; an empty Counter difference means yes

LeetCode 374 note: adjust the range by guess’s result, where -1 means the guess is too high and 1 too low

LeetCode 367 note: binary search [1, num] for mid² == num without using sqrt

LeetCode 350 note: an intersection keeping multiplicity, where Counter’s & takes the smaller count from each side