String Index Partition Mapping (Minimum Partitions after Deletion)

Coding: Represent string b using indexed substring partitions from a Given two strings a and b, select several contiguous ranges in a. Concatenate the corresponding substrings in order to form exactly b. A range is represented as [l, r] (1-based, l <= r) meaning substring a[l..r]. Return a list of ranges parts = [[l1,r1],[l2,r2],...] such that: a[l1..r1] + a[l2..r2] + ... == b If multiple solutions exist, return one with the minimum number of ranges (minimum partitions). If impossible, return an empty list. Example Input: a = "abcdbcd" b = "sabcd" Output (one possible): [[1,3],[4,4],[2,4]] The original anecdote example may not be fully consistent; rely on the formal rules above. Follow-up Delete one character (you may choose the position to improve the result), then recompute and return the minimum-partition representation. State whether you delete from a or from b and implement accordingly. Constraints (reasonable assumptions allowed) 1 <= len(a), len(b) <= 2e5 Character set: lowercase letters or printable ASCII I/O (stdin/stdout) stdin: two lines: a, then b stdout: first line: minimum number of partitions k (-1 if impossible) next k lines: l r per partition Example Input abcdbcd abcd Output 2 1 4 5 7