Daily Coding Problem Solutions

This is collection of .Net solutions to problems set by Daily Coding Problems. They are interview questions set by the likes of Google, Facebook, Amazon, etc.

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Daily Coding Problem - PrefixMapSum

This problem was asked by Google.

Implement a PrefixMapSum class with the following methods:

• insert(key: str, value: int): Set a given key's value in the map. If the key already exists, overwrite the value.
• sum(prefix: str): Return the sum of all values of keys that begin with a given prefix.

For example, you should be able to run the following code:

mapsum.insert("columnar",3)
assert mapsum.sum("col")==3
mapsum.insert("column",2)
assert mapsum.sum("col")==5

Solution

Daily Coding Problem - Rand5()

This problem was asked by Two Sigma.

Using a function rand7() that returns an integer from 1 to 7 (inclusive) with uniform probability, implement a function rand5() that returns an integer from 1 to 5 (inclusive).

Solution

Daily Coding Problem - Binary Tree Deepest Node

This problem was asked by Google.

Given the root of a binary tree, return a deepest node. For example, in the following tree, return d.

 a
/ \
b c
/
d

Solution

Roman Numerals

Write a function to convert Arabic numbers to Roman numerals.

Given a positive integer number (for example, 42), determine its Roman numeral representation as a string (for example, XLII).

Examples:

Simple numbers

Arabic	Roman	Arabic	Roman
1	I	60	LX
2	II	70	LXX
3	III	80	LXXX
4	IV	90	XC
5	V	100	C
6	VI	200	CC
7	VII	300	CCC
8	VIII	400	CD
9	IX	500	D
10	X	600	DC
20	XX	700	DCC
30	XXX	800	DCCC
40	XL	900	CM
50	L	1000	M

Composed Numbers

Arabic	Roman	Thousands	Cents	Tenths	Units
846	DCCCXLVI	-	DCC	XL	VI
1999	MCMXCIX	M	CM	XC	IX
2008	MMVIII	MM	-	-	VIII

Solution