Interview Q&A

Coding

Easy

Medium

Hard

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Brain Teasers

Easy

Sudoku Sub-Grid

Explain how you would fill in one 3x3 sub-grid in Sudoku algorithmically with each horizontal, vertical, and diagonal adding up to 15.

Example:

a	b	c
d	e	f
g	h	i

Horizontally:

1. a + b + c = 15
2. d + e + f = 15
3. g + h + i = 15

Vertically:

1. a + d + g = 15
2. b + e + h = 15
3. c + f + i = 15

Diagonally:

1. a + e + i = 15
2. g + e + c = 15

Explanation:

1. Find all of the possible combinations adding up to 15

⋅⋅⋅ 1 + 9 + 5, 2 + 8 + 5, 3 + 7 + 5, 4 + 6 + 5

2. Keep track of how many unique combinations each number can be apart of

⋅⋅⋅ In the above example, 5 is used 4 times

3. Note how many combinations each square requires

⋅⋅⋅|3|2|3| ⋅⋅⋅|:---|:---|:---| ⋅⋅⋅|2|4|2| ⋅⋅⋅|3|2|3|

Medium

Hard

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Theory/Technology