Welcome to Round 10 of the L19 Go Problem Championship.
All problems are black to play. As usual, provide your solutions either via hide tags, or direct private message to me.
Problem 1 (3 points)
$$Bc
$$ ------------------
$$ | . O . . . . O X .
$$ | O O . . O O O X .
$$ | X X O O X X X X .
$$ | . . X X . . . . .
$$ | . X . . . . . . .
$$ | . . . . . . . . .
[go]$$Bc
$$ ------------------
$$ | . O . . . . O X .
$$ | O O . . O O O X .
$$ | X X O O X X X X .
$$ | . . X X . . . . .
$$ | . X . . . . . . .
$$ | . . . . . . . . .[/go]
Problem 2 (6 points)
$$Bc
$$ --------------------
$$ . . O . . . . . . |
$$ . X X O . . O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |
[go]$$Bc
$$ --------------------
$$ . . O . . . . . . |
$$ . X X O . . O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |[/go]
Problem 3 (9 points)
$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O . O . X . .
$$ | . O . . O X X .
$$ | . . . . . O X .
$$ ----------------
[go]$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O . O . X . .
$$ | . O . . O X X .
$$ | . . . . . O X .
$$ ----------------[/go]
[go]$$B
$$ -------------------
$$ | . O . 3 . . O X .
$$ | O O 2 1 O O O X .
$$ | X X O O X X X X .
$$ | . B X X . . . . .
$$ | . . . . . . . . .[/go]
$$B
$$ --------------------
$$ . . O . . . 1 . . |
$$ . X X O . . O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |
[go]$$B
$$ --------------------
$$ . . O . . . 1 . . |
$$ . X X O . . O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |[/go]
$$Bc
$$ ------------------
$$ | . O . 3 . . O X .
$$ | O O 2 1 O O O X .
$$ | X X O O X X X X .
$$ | . . X X . . . . .
$$ | . X . . . . . . .
$$ | . . . . . . . . .
[go]$$Bc
$$ ------------------
$$ | . O . 3 . . O X .
$$ | O O 2 1 O O O X .
$$ | X X O O X X X X .
$$ | . . X X . . . . .
$$ | . X . . . . . . .
$$ | . . . . . . . . .[/go]
2.
The first intuition is
$$Bc
$$ --------------------
$$ . . O . . . . . . |
$$ . X X O . 1 O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |
[go]$$Bc
$$ --------------------
$$ . . O . . . . . . |
$$ . X X O . 1 O X X |
$$ . . . O . . O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |[/go]
However, W can resist at :4 and then make a ko:
$$Bc
$$ --------------------
$$ . . O . 0 7 3 6 9 |
$$ . X X O 5 1 O X X |
$$ . . . O 8 2 O O X |
$$ . X X O 4 X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |
[go]$$Bc
$$ --------------------
$$ . . O . 0 7 3 6 9 |
$$ . X X O 5 1 O X X |
$$ . . . O 8 2 O O X |
$$ . X X O 4 X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |[/go]
So B should destroy W's eye shape first:
$$Bc
$$ --------------------
$$ . . O . 4 . 3 . . |
$$ . X X O . 2 O X X |
$$ . . . O 5 1 O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |
[go]$$Bc
$$ --------------------
$$ . . O . 4 . 3 . . |
$$ . X X O . 2 O X X |
$$ . . . O 5 1 O O X |
$$ . X X O . X O X . |
$$ . . . O O O X . . |
$$ . . X X X X . X . |
$$ . . . . . . . . . |[/go]
3.
The intuition is a ko:
$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O . O . X . .
$$ | . O 1 . O X X .
$$ | 4 3 2 5 . O X .
$$ ----------------
[go]$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O . O . X . .
$$ | . O 1 . O X X .
$$ | 4 3 2 5 . O X .
$$ ----------------[/go]
Variation:
$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | 6 O 7 O . X . .
$$ | 5 O 1 . O X X .
$$ | . 3 2 4 . O X .
$$ ----------------
[go]$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | 6 O 7 O . X . .
$$ | 5 O 1 . O X X .
$$ | . 3 2 4 . O X .
$$ ----------------[/go]
[go]$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O . O . X . .
$$ | . O 1 6 O X X .
$$ | 4 3 2 5 . O X .
$$ ----------------[/go]
For example:
$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O 8 O . X . .
$$ | . O 1 6 O X X .
$$ | 4 7 C 5 . O X .
$$ ----------------
[go]$$Bc
$$ | . . . . . . . .
$$ | . X X X X . . .
$$ | X O . , . X . .
$$ | . O 8 O . X . .
$$ | . O 1 6 O X X .
$$ | 4 7 C 5 . O X .
$$ ----------------[/go]