a). let's assume the set of the following conditions;
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b). if group with "9" would begin from the left edge in line 7 it will reach the cell marked "X";
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c). if group with "9" would begin from the right edge it will reach the cell marked "Z";
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d). it is logically that all squares between cells marked "X" and "Z" will be filled. Let's do the same with lines with numbers "9" and "10".
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e). according to logic that described above let's worked out columns with numbers "3", "6", "7" and etc. While solving you must not forget to mark the cells that would never be filled.
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f). it's easy to complete solution being bottomed on simple logic.
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