LeetCode

LeetCode 1833 note: buy the cheapest first; the problem asks for counting sort, and with values up to 10^5 each price buys min(count, coins // price)

LeetCode 307 note: point updates with range sums make prefix sums O(n) per update; a segment tree or Fenwick tree makes both operations O(log n)

LeetCode 3961 note: every device but one donates its smallest unit to the same device; that device’s rating becomes the global minimum, so pick the one with the smallest second-smallest value

LeetCode 3960 note: n is only 1000, so fix the left end and extend right while maintaining value -> count and count -> how many; exactly two counts f and 2f means balanced

LeetCode 3959 note: accumulate the square sum minus the digit sum; each digit adds d² − d ≥ 0, so the gap never shrinks and you can return as soon as it reaches 50

LeetCode 3952 note: each token moves left at most once, so the state is whether this index’s token moved left; moving only helps if the index to the left was not already covered

LeetCode 3951 note: a bulb lights at most 3 positions, so each time unit needs ceil(brightness / 3) bulbs; merge the intervals for the total time and multiply

LeetCode 3950 note: each 1 in n & (n » 1) marks a pair of adjacent ones, so exactly one pair means it has a single 1

LeetCode note for Domino and Tromino Tiling, rebuilt from the original learning note

LeetCode note for Paint Fence, rebuilt from the original learning note

LeetCode note for Minimum Swaps To Make Sequences Increasing, rebuilt from the original learning note

LeetCode note for Wiggle Subsequence, rebuilt from the original learning note