Task $2$

Java $8$

There is a board made of two rows and $N$ columns. The board is represented by two strings, row$1$ and row$2,$ made of characters $\text{'}R\text{'},\text{'}W\text{'}$ and$/$or $\text{'}?\text{'}.$ A board is balanced if$,$ in each row and in each column, the number of characters $\text{'}R\text{'}$ is equal to the number of characters $\text{'}W\text{'}.$ For example, the following board is balanced:

$?$RW$?$WR

$?$WR$?$RW

and the following board is not balanced:

W$?$WR$?$

R$??$W$?$

$($there are two characters $\text{'}W\text{'}$ and one character $\text{'}R\text{'}$ in the first row$).$

The question marks $(\text{'}?\text{'})$ can be replaced with $\text{'}W\text{'}$ or $\text{'}R\text{'}.$ What is the minimum number of replacements needed to balance the board?

Write a function:

class Solution $\{$ public int solution$($String row$1,$ String row$2)$ ; $\}$

that, given two strings row$1$ and row$2$ made of $N$ characters each, returns the minimum number of replacements needed to balance the board. If it is not possible to balance the board, the function should return $-1.$

$14C$

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