Two-Pointers

LeetCode 1147 note: build strings inward from both ends and cut a pair as soon as they match; cutting early is best, and any leftover middle counts as one chunk

LeetCode 522 note: the longest uncommon subsequence is always a whole string; check strings from longest to shortest, and the first that is not a subsequence of any other long-enough string is the answer

LeetCode 1826 note: at the first mismatch, test both “who dropped a value” explanations; if both fit, it cannot be determined, so return -1

LeetCode 3884 note: compare from both ends toward the middle; the first match is the answer, and odd lengths always match in the middle

LeetCode 1023 note: two pointers character by character; anything beyond the pattern must be lowercase

LeetCode 1570 note: store only non-zero (index, value) pairs, and compute the dot product by merging the two index-sorted lists with two pointers, multiplying only on equal indices

LeetCode 1229 note: sort both people’s slots, then find intersections with two pointers as in 986; the first intersection that is long enough is the earliest slot

LeetCode 244 note: precompute each word’s positions (sorted by construction), then answer each query by merging the two position lists with two pointers, always advancing the smaller one

LeetCode 986 note: two pointers each hold an interval, the intersection is [max(starts), min(ends)], and the interval that ends first cannot meet anything else, so its pointer advances

LeetCode 777 note: XL→LX moves L left and RX→XR moves R right; after skipping X the order must match, with L only moving left and R only moving right

LeetCode 2337 note: after skipping blanks the piece order must match; L only moves left and R only moves right, so each L’s start index must be >= its target index and each R’s must be <=

LeetCode 1537 note: two sorted arrays can switch only at shared values; merge with two pointers, keep a running sum per path, and at a shared value set both to the larger sum plus that value