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Rev

Required fields*

Verify a Minesweeper board

Your goal is to check whether a completed Minesweeper board is valid. This means that each number is a correct count of mines in cells adjacent to it, including diagonals. The board does not wrap around.

As usual, you should give a function or program, and shortest code in bytes wins.

See also past challenges to generate, solve, and fully implement Minesweeper.

Input:

A single string like this: 02X2 13X2 X211.

The rows of the minesweeper board are given separated by spaces. So, the above represents the 3x4 board:

02X2
13X2
X211
Each cell is a character: X for a mine, or a number 0 through 8.
All rows have the same length.
There are at least 3 rows and 3 columns.
The input doesn't start or end with a space, but you may include a newline at the end if you wish.

Output:

A consistent Truthy on correct boards, and a consistent Falsey value on incorrect boards. Consistent means that all Truthy outputs are the same and all Falsey outputs are the same.

Test cases

Each line is a separate test case.

True:

02X2 13X2 X211
XXXX XXXX XXXX XXXX
XX4X2 5X6X4 XX6XX 4XX54 2X4XX

False:

02X2 13X2 X212
XXXX XXXX X7XX XXXX
XX5X2 5X6X4 XX6XX 4XX54 2X5XX

Answer*

# R, 156 chars

a=b=do.call(rbind,strsplit(scan(,""),""));for(i in 1:nrow(a))for(j in 1:ncol(a))b[i,j]=sum(a[abs(i-row(a))<2&abs(j-col(a))<2]=="X");v=a!="X";all(b[v]==a[v])

With indents, spaces and line breaks, for legibility:

a = b = do.call(rbind,strsplit(scan(,""),"")) #Reads stdin and turn into a matrix
    for(i in 1:nrow(a)) #Ugly, ugly loop
        for(j in 1:ncol(a))
            b[i,j] = sum(a[abs(i-row(a))<2 & abs(j-col(a))<2]=="X")
    v = a!="X"
    all(b[v]==a[v])

Examples:

> a=b=do.call(rbind,strsplit(scan(,""),""));for(i in 1:nrow(a))for(j in 1:ncol(a))b[i,j]=sum(a[abs(i-row(a))<2&abs(j-col(a))<2]=="X");v=a!="X";all(b[v]==a[v])
    1: XX4X2 5X6X4 XX6XX 4XX54 2X4XX
    6: 
    Read 5 items
    [1] TRUE
    > a=b=do.call(rbind,strsplit(scan(,""),""));for(i in 1:nrow(a))for(j in 1:ncol(a))b[i,j]=sum(a[abs(i-row(a))<2&abs(j-col(a))<2]=="X");v=a!="X";all(b[v]==a[v])
    1: XXXX XXXX XXXX XXXX
    5: 
    Read 4 items
    [1] TRUE
    > a=b=do.call(rbind,strsplit(scan(,""),""));for(i in 1:nrow(a))for(j in 1:ncol(a))b[i,j]=sum(a[abs(i-row(a))<2&abs(j-col(a))<2]=="X");v=a!="X";all(b[v]==a[v])
    1: XX5X2 5X6X4 XX6XX 4XX54 2X5XX
    6: 
    Read 5 items
    [1] FALSE

If this is an answer to a challenge…

…Be sure to follow the challenge specification. However, please refrain from exploiting obvious loopholes. Answers abusing any of the standard loopholes are considered invalid. If you think a specification is unclear or underspecified, comment on the question instead.
…Try to optimize your score. For instance, answers to code-golf challenges should attempt to be as short as possible. You can always include a readable version of the code in addition to the competitive one. Explanations of your answer make it more interesting to read and are very much encouraged.
…Include a short header which indicates the language(s) of your code and its score, as defined by the challenge.

More generally…

…Please make sure to answer the question and provide sufficient detail.
…Avoid asking for help, clarification or responding to other answers (use comments instead).

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