Write code in C$++$ Also, check for the corner cases. There is a cleaning robot which is cleaning a rectangular grid of size N x M$,$ represented by array R consisting of N strings. Rows are numbered from $0$ to N$-1($from top to bottom$)$ and columns are numbered from $0$ to M$-1($from left to right$).$ The robot starts cleaning in the top$-$left corner, facing rightwards. It moves in a straight line for as long as it can, i$.$e$.$ while there is an unoccupied grid square ahead of it$.$ When it cannot move forward, it rotates $90$ degrees clockwise and tries to move forward again until it encounters another obstacle, and so on$.$ Dots in the array $(".")$ represent empty squares and $"$X$"$s represent occupied squares $($ones the robot cannot move through$).$ Each square that the robot occupied at least once is considered clean. The robot moves indefinitely. Write a function: int solution $($vector &R$)$; that, given an array R consisting of N strings, each of length M$,$ representing the grid, returns the number of clean squares. Examples: $1.$ Given A$=["...$ X $...,",...$ X X $","..$ X$..."],$ your function should return $6./$r$/$n $1.$ Given A$=["...$ X $...,......$ X X$^*,...$ X $....]$ your function should return $6.$The robot starts at $(0,0),$ facing rightwards, and moves to $(0,2),$ where it turns due to the obstacle at $(0,3).$ Then it goes down from $(0,2)$ to $(1,2),$ where it changes direction again due to another obstacle. Next it goes left from $(1,2)$ to $(1,0),$ where it turns once because of the grid boundary, then it moves once and turns once more, which makes it stand again at position $(0,0)$ facing rightwards, just as at the beginning, which means it will now repeat the loop indefinitely. The total number of cleaned squares is $6.2.$ Given A$=["....$ x $..","$ X $.....","....$ x $.",".......",$ your function should return $15./$r$/$n $2.$ Given A$=["....$ X $...,"$ X $.....,"....$ X $.",........]$ your function should return $15.3.$ Given A$=["....$ X $.",".$ X $....,","$X$...$X$","..$X$.."],$ your function should return $9.4.$ Given A$=["."],$ your function should return $1,$ because there is only one square on the grid and it is cleaned in the first move. Assume that: $-$ N and M are integers within the rance $[1.\mathrm{.}201$: $/$r$/$n $4.$ Given A$=["..],$ your function should return $1,$ because there is only one square on the grid and it is cleaned in the first move. Assume that: $-$ N and M are integers within the range $[1.\mathrm{.}20]$; $-$ top$-$left cell is empty; $-$ each string in R consists only of the following characters: $"."$ and$/$or $"$X$".$ In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.