LeetCode

LeetCode 1078 note: split into words and check every three consecutive words, collecting the third when the first two match

LeetCode 1051 note: sort and count the positions that differ from the original

LeetCode 1047 note: if the stack top equals the current character both vanish, otherwise push it; after a removal the new top may cancel with the next character

LeetCode 1046 note: from a max-heap (negated values) take the two heaviest each round, push back their difference if unequal, and return the last stone or 0

LeetCode 1030 note: list every coordinate and sort by Manhattan distance to the center; return coordinates, not distances

LeetCode 997 note: the judge is trusted by the other n - 1 people and trusts nobody, so in-degree minus out-degree equals n - 1

LeetCode 1025 note: dp[i] holds when some divisor x of i makes dp[i - x] a loss; observing the pattern, the answer is simply whether n is even

LeetCode 1022 note: on the way down double the current number and add the node’s bit, adding it to the total at a leaf

LeetCode 1021 note: track depth instead of a stack; the ‘(’ raising depth from 0 to 1 and the ‘)’ lowering it from 1 to 0 are outermost, everything else stays

LeetCode 1018 note: each new bit turns the prefix into x = 2x + bit, so keep only x mod 5 and the number never grows

LeetCode 1013 note: the total must be divisible by 3; accumulate from the left, cutting whenever the running sum hits total / 3, and succeed with at least 3 pieces

LeetCode 1005 note: negate the smallest value each time; once the smallest is positive, only the parity of the remaining count matters