Spell a word with letter blocks, one block per letter

You have a set of letter blocks. Each block is a list of lowercase characters printed on its faces. You also get a target string.

Implement can_form(blocks: list[list[str]], target: str) -> bool. Return True if you can spell target by taking one character from a block for each position of target, where:

• each block is used for at most one position,
• the blocks can be used in any order, and
• a block that shows the same letter twice still counts as one block.

Constraints: 0 <= len(target) <= 1000, 0 <= len(blocks) <= 1000, each block has 1 to 26 characters.

Example 1

blocks = [["m", "q"], ["o", "p"], ["p", "m"]]
target = "mop"
-> True   # m from block 0, o from block 1, p from block 2

Example 2

blocks = [["r", "s"], ["r"], ["t"]]
target = "rrs"
-> False  # only two blocks have 'r', and one of them is also the only block with 's'

A natural follow-up: return which block is used for each position of target.

Reconstructed from the reported question; details may differ from what interviewers ask.