What is the pattern?

Trick to solve this: Read out loud the number in the row. The speech will be the next number.

For example, $1$ is read as " one number one ", so $11$ will be the next number.

$11$ is read as " two number one ", so $21$ will be the next number.

$21$ is read as " one number two , one number one ", so $1211$ will be the next number.

$1211$ is read as " one number one , one number two , two number one ", so $111221$ will be the next number.

Applying the same method, $1112211$ is read as " three number one , two number two , one number one ", so $\boxed{312211}$ will be the answer.

In each row, 1 is added to both sides

Therefore next row will be 11112211

Now, sum of all consecutive 1s in a row is taken but the freshly added 1s are not counted.

Therefore final answer will be

1 1+1+1 22 11

First and last 1 will not be added as they are new

Therefore answer is 312211