Array

LeetCode 118 note: each row starts and ends with 1, and every inner cell is the sum of the two cells above it

LeetCode 108 note: the middle element becomes the root and each half recurses; the halves differ by at most one, so the tree is balanced

LeetCode 66 note: add one from the last digit, turning 9s into 0s while carrying, and prepend 1 when every digit was 9

LeetCode 35 note: find the first position >= target (lower bound); a half-open [l, r) needs r = mid, not r = mid - 1

LeetCode 27 note: the write pointer copies only values not equal to val, returning how many were written

LeetCode 26 note: overwrite in place with a write pointer for the next slot, writing only values different from the last one written

LeetCode 14 note: bound by the shortest string and check each position across all strings; the first mismatch gives the answer’s length

LeetCode 1 note: store seen numbers in a hash map while scanning and look up target - x; checking before storing prevents using one element twice