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added 34 characters in body

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edited Jan 20, 2018 at 15:35

#Ruby 8989 79 bytes -10 bytes thanks to Unihedron

->m{n=m.map &:dup;3n=m;3.times{n=n.zip(m=m.transpose.reverse).map{|i,j|i.zip(j).map &:sum}};n}

#Ruby 89 bytes

->m{n=m.map &:dup;3.times{n=n.zip(m=m.transpose.reverse).map{|i,j|i.zip(j).map &:sum}};n}

#Ruby 89 79 bytes -10 bytes thanks to Unihedron

->m{n=m;3.times{n=n.zip(m=m.transpose.reverse).map{|i,j|i.zip(j).map &:sum}};n}

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created Jan 20, 2018 at 12:08

#Ruby 89 bytes

->m{n=m.map &:dup;3.times{n=n.zip(m=m.transpose.reverse).map{|i,j|i.zip(j).map &:sum}};n}