For the first time, put 1-4 on the left and 5-8 on the right.

1. If the weight is right, the bad ball is in 1-8.

Remove No.2-4 for the second time, move No.6-8 from right to left, and put No.9-11.

It's on the right. That is to say, put 1, 6, 7, 8 on the left and 5, 9, 10,1/on the right.

1. If the weight, the bad ball in the untouched 1, 5. If it is 1,

It is lighter than the standard ball; If it's a No.5 ball, it's heavier than the standard ball.

Put 1 on the left and No.2 on the right for the third time.

1. If the weight is appropriate, 1 is a bad ball, which is lighter than the standard ball;

2. If it is balanced, the 5th ball is a bad ball, which is heavier than the standard ball;

It can't be left-handed this time.

2. If it is balanced, the bad ball is lighter than the standard ball in the number 2-4 that has been removed.

Put No.2 on the left and No.3 on the right for the third time.

1. If the weight is appropriate, the No.2 ball is a bad ball, which is lighter than the standard ball;

2. If it is balanced, the No.4 ball is a bad ball and lighter than the standard ball;

3. If the left is heavy, No.3 is a bad ball, which is lighter than the standard ball.

3. If the left ball is heavy, the bad ball will be taken to the left 6-8, which is heavier than the standard ball.

For the third time, put No.6 on the left and No.7 on the right.

1. If the weight is appropriate, No.7 is a bad ball, which is heavier than the standard ball;

2. If it is balanced, the No.8 ball is a bad ball and heavier than the standard ball;

3. If the left ball is heavy, No.6 is a bad ball, which is heavier than the standard ball.

2. If the balance is balanced, the bad ball is 9- 12.

The second time, put 1-3 on the left and 9- 1 1 on the right.

1. If the weight is appropriate, the bad ball is 9- 1 1, and the bad ball is heavier.

Put No.9 on the left and 10 on the right for the third time.

1. If the weight is appropriate, 10 is a bad ball, which is heavier than the standard ball;

2. If it is balanced, the number 1 1 is a bad ball, which is heavier than the standard ball;

3. If the left ball is heavy, No.9 is a bad ball, which is heavier than the standard ball.

2. If it is balanced, the bad ball is 12.

For the third time, put 1 on the left and 12 on the right.

1. If the weight is appropriate, 12 is a bad ball, which is heavier than the standard ball;

2. It is impossible to balance at this time;

3. If the left ball is heavy, the number 12 is a bad ball, which is lighter than the standard ball.

3. If the left is heavy, the bad ball is 9- 1 1, and the bad ball is lighter.

Put No.9 on the left and 10 on the right for the third time.

1. If the weight is appropriate, the No.9 ball is a bad ball, which is lighter than the standard ball;

2. If it is a balance ball, the number 1 1 is a bad ball, which is lighter than the standard ball;

3. If the left ball is heavy, 10 is a bad ball, which is lighter than the standard ball.

3. If the left is heavy, the bad ball is in 1-8.

Remove No.2-4 for the second time, move No.6-8 from right to left, and put No.9-11.

It's on the right. That is to say, put 1, 6, 7, 8 on the left and 5, 9, 10,1/on the right.

1. If the right ball is heavy, the bad ball will be taken to the left 6-8, which is lighter than the standard ball.

For the third time, put No.6 on the left and No.7 on the right.

1. If the weight is appropriate, No.6 is a bad ball, which is lighter than the standard ball;

2. If it is a balance ball, the No.8 ball is a bad ball, which is lighter than the standard ball;

3. If the left is heavy, No.7 is a bad ball, which is lighter than the standard ball.

2. If it is balanced, the bad ball is heavier than the standard ball in the number 2-4 that has been removed.

Put No.2 on the left and No.3 on the right for the third time.

1. If the weight is appropriate, the No.3 ball is a bad ball, which is heavier than the standard ball;

2. If it is balanced, No.4 is a bad ball, which is heavier than the standard ball;

3. If the left ball is heavy, No.2 is a bad ball, which is heavier than the standard ball.

3. If the left is heavy, the bad ball is at the untouched number 1, 5. If it is 1,

It is heavier than the standard ball; If it's a No.5 ball, it's lighter than the standard ball.

Put 1 on the left and No.2 on the right for the third time.

1. It can't be right this time.

2. If it is balanced, the No.5 ball is a bad ball and lighter than the standard ball;

3. If the left ball is heavy, then the number 1 is a bad ball, which is heavier than the standard ball.