Evaluate word-guess feedback with repeats

You are implementing feedback for a Wordle-like guessing game.

Part 1 — Produce feedback for one guess

You are given two strings of equal length guess and target (lowercase letters). For each index i, output a status character:

• G (green): guess[i] == target[i]
• Y (yellow): guess[i] != target[i] , and the letter guess[i] occurs in target in some position not already matched by a G , respecting multiplicity (i.e., each occurrence in target can be used at most once across all Y assignments).
• W (white/gray): otherwise.

Return a string of length n over {G,Y,W}.

Examples

• guess = "cable" , target = "maple" → WGWGG
• guess = "paple" , target = "maple" → WGGGG
• guess = "apple" , target = "maple" → YWGGG

Part 2 — Validate future guesses using past information

Now the same target is used for multiple rounds. After each evaluated guess, you “learn” some letters are impossible.

A future guess is considered invalid_input if it contains any letter that was previously confirmed to be absent from target.

Clarification for repeated letters: a letter should be considered “confirmed absent” only if, in some previous round, all occurrences of that letter in that guess were marked W (i.e., the letter never appeared as G or Y in that round).

Example

Round 1: guess = "cable", target = "maple" → WGWGG

• Letters confirmed absent: c , b .

Round 2: guess = "cazle", target = "maple" → return invalid_input (contains c, which was confirmed absent).

Implement the evaluator for Part 1 and the validator logic for Part 2.

Constraints (reasonable assumptions)

• 1 <= n <= 10^5 (design an efficient solution)
• guess.length == target.length
• Strings contain only lowercase English letters.