L19 Go Problem Championship: Round 2

Kirby · Post by **Kirby** » Thu Feb 23, 2017 10:52 pm

Welcome to Round 2 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)

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X . . . . . $$ | . O X . . . . . $$ | . O X , . . . . $$ | . X O X . . . . $$ | . O O X . X . . $$ | . . . . . . . . $$ ----------------[/go]

Problem 2 (6 points)

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | . O . . . O X . $$ | . . . . O . . . $$ ----------------[/go]

Problem 3 (9 points)

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , . . O . X , $$ | . . . X O . . O X . $$ | . X . X O . . O X . $$ | . . . . . . . O . . $$ --------------------[/go]

Have fun!

EdLee · Post by **EdLee** » Fri Feb 24, 2017 5:13 am

2017 Round 2.1 (004)

Click Here To Show Diagram Code: [go]$$B B kills $$ | . . . . . . . . $$ | . X X . . . . . $$ | . O X . . . . . $$ | 4 O X , . . . . $$ | 1 X O X . . . . $$ | 2 O O X . X . . $$ | . 5 3 . . . . . $$ ----------------[/go]

2017 Round 2.2 (005)

Click Here To Show Diagram Code: [go]$$B First feelings: (a) or (b) $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | a O . . . O X . $$ | . b . . O . . . $$ | ---------------[/go]

Hane:

Clamp:

Click Here To Show Diagram Code: [go]$$B W dies $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 5 O 4 3 . O X . $$ | . 1 2 . O . . . $$ | ---------------[/go]

If

extends:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O . . . O X . $$ | . 1 3 . O . . . $$ | ---------------[/go]

Click Here To Show Diagram Code: [go]$$B W dies $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O . 4 . O X . $$ | . 1 3 . O . 5 . $$ | ---------------[/go]

Click Here To Show Diagram Code: [go]$$B W dies $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O . . . O X . $$ | . 1 3 4 O . 5 . $$ | ---------------[/go]

If

connects:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O 4 . . O X . $$ | . 1 3 . O . . . $$ | ---------------[/go]

Click Here To Show Diagram Code: [go]$$B W lives $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O 4 6 5 O X . $$ | . 1 3 . O . . . $$ | ---------------[/go]

Click Here To Show Diagram Code: [go]$$B :b5: @ (a) or (b): seki $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O 4 . 6 O X . $$ | . 1 3 a O . b . $$ | ---------------[/go]

2017 Round 2.3 (006)

Click Here To Show Diagram Code: [go]$$B W lives $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 3 1 2 O . X , $$ | . . . X O . . O X . $$ | . X . X O . . O X . $$ | . . . . 4 . . O . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$B W lives $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , . . O . X , $$ | . . . X O 2 . O X . $$ | . X . X O 1 . O X . $$ | . . . . . . . O . . $$----------------------[/go]

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , . . O . X , $$ | . . . X O 1 . O X . $$ | . X . X O . . O X . $$ | . . . . . . . O . . $$----------------------[/go]

Kirby · Post by **Kirby** » Fri Feb 24, 2017 9:23 am

@EdLee:

Lanrose · Post by **Lanrose** » Fri Feb 24, 2017 9:57 am

Kirby · Post by **Kirby** » Fri Feb 24, 2017 11:02 am

@Lanrose:

Lanrose · Post by **Lanrose** » Fri Feb 24, 2017 3:27 pm

@Kirby

Kirby · Post by **Kirby** » Fri Feb 24, 2017 4:42 pm

@Lanrose:

jeromie · Post by **jeromie** » Fri Feb 24, 2017 8:36 pm

Problem 1

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X . . . . . $$ | . O X . . . . . $$ | . O X , . . . . $$ | 1 X O X . . . . $$ | 2 O O X . X . . $$ | . a 3 . . . . . $$ ----------------[/go]

White can't play at a for a second eye due to a shortage of liberties

Problem 2

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | a O . c . O X . $$ | . b . . O . . . $$ ----------------[/go]

This reminds me of this problem Bill Spight posted a while back. But there's a crucial difference; if black hanes at a here and white decends at b, the resulting shape is dead instead of alive. That suggests to me that black can do better than ko in this problem and that c is a key point.

Here's my answer:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 2 O 4 1 3 O X . $$ | . . . . O 5 . . $$ ----------------[/go]

Another possible resistance:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 5 O 3 1 4 O X . $$ | . . . 2 O . . . $$ ----------------[/go]

Problem 3 (9 points)

I think this clamp works:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , . . O . X , $$ | . . . X O 3 . O X . $$ | . X . X O 1 . O X . $$ | . . . . 2 a . O . . $$ --------------------[/go]

The hane at a is answered by the same 3.

If white tries this

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , b . O a X , $$ | . . . X O 2 . O X . $$ | . X . X O 1 4 O X . $$ | . . . 7 3 5 6 O . $$ --------------------[/go]

The weakness at a and the shortage of liberties at b ensure white can't get two eyes.

jeromie · Post by **jeromie** » Fri Feb 24, 2017 8:51 pm

gamesorry · Post by **gamesorry** » Fri Feb 24, 2017 11:11 pm

1.

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X . . . . . $$ | . O X . . . . . $$ | . O X , . . . . $$ | 1 X O X . . . . $$ | 2 O O X . X . . $$ | . a 3 . . . . . $$ ----------------[/go]

2.

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 3 O 2 1 . O X . $$ | . . . . O . . . $$ ----------------[/go]

Incidentally, I just found a very similar situation in one of my 13*13 games today:
https://online-go.com/game/6863138 (move 53)

Variation 1: Ko, B fails

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . $$ | . X X X X . . . $$ | . X O O O X X . $$ | 1 O . 2 . O X . $$ | . 3 4 . O . . . $$ ----------------[/go]

3.

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , 4 . O . X , $$ | . . . X O 7 2 O X . $$ | . X . X O 3 1 O X . $$ | . . . . 6 5 . O . . $$ --------------------[/go]

Variation:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 4 . 7 O . X , $$ | . . . X O . 2 O X . $$ | . X . X O 3 1 O X . $$ | . . . . 5 6 . O . . $$ --------------------[/go]

Variation:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 9 . 4 O 5 X , $$ | . . . X O . 3 O X . $$ | . X . X O . 1 O X . $$ | . . . . 2 8 6 O 7 . $$ --------------------[/go]

Variation:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X , 5 . O . X , $$ | . . . X O 4 3 O X . $$ | . X . X O 2 1 O X . $$ | . . . . . . . O . . $$ --------------------[/go]

Variation:

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 7 5 6 O 4 X , $$ | . . . X O a 3 O X . $$ | . X . X O 2 1 O X . $$ | . . . . 8 . 9 O . . $$ --------------------[/go]

B fails

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 4 . . O . X , $$ | . . . X O 2 8 O X . $$ | . X . X O 1 3 O X . $$ | . . . . 5 6 7 O . . $$ --------------------[/go]

B fails

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . . . . $$ | . . . X X X . . . . $$ | . . X O O O X X . . $$ | . . X 3 1 2 O . X , $$ | . . . X O . . O X . $$ | . X . X O . . O X . $$ | . . . . 4 . . O . . $$ --------------------[/go]

Kirby · Post by **Kirby** » Sat Feb 25, 2017 4:12 pm

@jeromie:

Kirby · Post by **Kirby** » Sat Feb 25, 2017 4:14 pm

@gamesorry:

Shaddy · Post by **Shaddy** » Sat Feb 25, 2017 9:23 pm

gamesorry · Post by **gamesorry** » Sat Feb 25, 2017 9:50 pm

Kirby · Post by **Kirby** » Sat Feb 25, 2017 10:19 pm

@Shaddy:

Life In 19x19

L19 Go Problem Championship: Round 2

L19 Go Problem Championship: Round 2

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Re: L19 Go Problem Championship: Round 2

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Re: L19 Go Problem Championship: Round 2

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Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

Re: L19 Go Problem Championship: Round 2

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