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https://github.com/farida-hamid/practice


https://github.com/farida-hamid/practice

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# Practice



## 1. [Two Sum](https://leetcode.com/problems/two-sum/)

Given an array of integer nums and an integer target, I built a function that returns indices of the two numbers such that they add up to the target without using the same element twice. I assumed that each input would have exactly one solution.



#### Example 1:

    Input: nums = [2,7,11,15], target = 9

    Output: [0,1]

    

#### Example 2:

    Input: nums = [3,2,4], target = 6

    Output: [1,2]

    

#### Example 3:  

    Input: nums = [3,3], target = 6

    Output: [0,1]



## 2. [Palindrome Number](https://leetcode.com/problems/palindrome-number/)



Given an integer x, I built a function that returns true if x is a palindrome, and false otherwise. An integer is a palindrome when it reads the same forward and backward. For example, 121 is a palindrome while 123 is not.



#### Example 1:

    Input: x = 121

    Output: true

    Explanation: 121 reads as 121 from left to right and from right to left.



#### Example 2:

    Input: x = -121

    Output: false

    Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.



#### Example 3:

    Input: x = 10

    Output: false

    Explanation: Reads 01 from right to left. Therefore it is not a palindrome.



## 3. [Roman to Integer](https://leetcode.com/problems/roman-to-integer/)

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.



    Symbol       Value

    I             1

    V             5

    X             10

    L             50

    C             100

    D             500

    M             1000

For example, 2 is written as II in Roman numeral, just two ones added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.



Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:



I can be placed before V (5) and X (10) to make 4 and 9. 

X can be placed before L (50) and C (100) to make 40 and 90. 

C can be placed before D (500) and M (1000) to make 400 and 900.

Given a roman numeral, convert it to an integer.



#### Example 1:

    Input: s = "III"

    Output: 3

    Explanation: III = 3.



#### Example 2:

    Input: s = "LVIII"

    Output: 58

    Explanation: L = 50, V= 5, III = 3.



#### Example 3:

    Input: s = "MCMXCIV"

    Output: 1994

    Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.



## 4. Array Quadruplet



Given an unsorted array of integers and a number, I wrote a function findArrayQuadruplet that finds four numbers (quadruplets) in the array that sum up to the given number. The function should return an array of these numbers in ascending order. If such a quadruplet doesn’t exist, empty array otherwise.



There may be more than one quadruplet in the array that sum to the given number. I will return the first one you encounter (considering the results are sorted).



#### Example:



    input:  arr = [2, 7, 4, 0, 9, 5, 1, 3], s = 20

    output: [0, 4, 7, 9]



## 5. Smallest Substring of All Characters



Given an array of unique characters arr and a string str, I implemented the function getShortestUniqueSubstring that finds the smallest substring of str containing all the characters in arr and returns an empty string if such a substring doesn’t exist.



#### Example:



    input:  arr = ['x','y','z'], str = "xyyzyzyx"

    output: "zyx"



## 6. [Number Line Jumps](https://www.hackerrank.com/challenges/kangaroo/problem)

You are choreographing a circus show with various animals. For one act, you are given two kangaroos on a number line ready to jump in the positive direction (i.e, toward positive infinity).

- The first kangaroo starts at location  and moves at a rate of  meters per jump.

- The second kangaroo starts at location  and moves at a rate of  meters per jump.

You have to figure out a way to get both kangaroos at the same location at the same time as part of the show. If it is possible, return YES, otherwise return NO.



#### Example 1:

    Input: 0 3 4 2

    Output: YES



#### Example 2:

    Input: 0 2 5 3

    Output: NO



## 7. [Viral Advertising](https://www.hackerrank.com/challenges/strange-advertising/copy-from/251554491)

HackerLand Enterprise is adopting a new viral advertising strategy. When they launch a new product, they advertise it to exactly 5 people on social media.

On the first day, half of those 5 people (i.e., floor(5/2) = 2) like the advertisement and each shares it with 3 of their friends. At the beginning of the second day, floor(5/2) * 3 = 6 people receive the advertisement.

Each day, floor(recipients / 2) of the recipients like the advertisement and will share it with 3 friends on the following day. Assuming nobody receives the advertisement twice, determine how many people have liked the ad by the end of a given day, beginning with launch day as day 1.

#### Example 

    n = 5

    Day Shared Liked Cumulative

    1      5     2       2

    2      6     3       5

    3      9     4       9

    4     12     6      15

    5     18     9      24

The progression is shown above. The cumulative number of likes on the fifth day is 24.

#### Function Description

Complete the viralAdvertising function in the editor below.

viralAdvertising has the following parameter(s):

int n: the day number to report

#### Returns

int: the cumulative likes at that day

#### Input Format

A single integer, n, the day number.



## 8. [Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)

Write a function to find the longest common prefix string amongst an array of strings.



If there is no common prefix, return an empty string "".



#### Example 1:



    Input: strs = ["flower","flow","flight"]

    Output: "fl"

#### Example 2:



    Input: strs = ["dog","racecar","car"]

    Output: ""

    Explanation: There is no common prefix among the input strings.



## 9. [Plus One]( https://leetcode.com/problems/plus-one/description/)



You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0's.



Increment the large integer by one and return the resulting array of digits.



#### Example 1:

    Input: digits = [1,2,3]

    Output: [1,2,4]

    Explanation: The array represents the integer 123.

    Incrementing by one gives 123 + 1 = 124.

    Thus, the result should be [1,2,4].



#### Example 2:

    Input: digits = [4,3,2,1]

    Output: [4,3,2,2]

    Explanation: The array represents the integer 4321.

    Incrementing by one gives 4321 + 1 = 4322.

    Thus, the result should be [4,3,2,2].



#### Example 3:

    Input: digits = [9]

    Output: [1,0]

    Explanation: The array represents the integer 9.

    Incrementing by one gives 9 + 1 = 10.

    Thus, the result should be [1,0].



## 10. [Apple and Orange](https://www.hackerrank.com/challenges/apple-and-orange/problem)

Sam's house has an apple tree and an orange tree that yield an abundance of fruit. Using the information given below, determine the number of apples and oranges that land on Sam's house.

In the diagram below:

The red region denotes the house, where  is the start point, and  is the endpoint. The apple tree is to the left of the house, and the orange tree is to its right.

Assume the trees are located on a single point, where the apple tree is at point , and the orange tree is at point .

When a fruit falls from its tree, it lands  units of distance from its tree of origin along the -axis. *A negative value of means the fruit fell  units to the tree's left, and a positive value of  means it falls  units to the tree's right. *

Apple and orange(2).png

Given the value of  for  apples and  oranges, determine how many apples and oranges will fall on Sam's house (i.e., in the inclusive range )?

For example, Sam's house is between  and . The apple tree is located at  and the orange at . There are  apples and  oranges. Apples are thrown  units distance from , and  units distance. Adding each apple distance to the position of the tree, they land at . Oranges land at . One apple and two oranges land in the inclusive range  so we print

1

2

Function Description

Complete the countApplesAndOranges function in the editor below. It should print the number of apples and oranges that land on Sam's house, each on a separate line.

countApplesAndOranges has the following parameter(s):

s: integer, starting point of Sam's house location.

t: integer, ending location of Sam's house location.

a: integer, location of the Apple tree.

b: integer, location of the Orange tree.

apples: integer array, distances at which each apple falls from the tree.

oranges: integer array, distances at which each orange falls from the tree.

Input Format

The first line contains two space-separated integers denoting the respective values of  and . 

The second line contains two space-separated integers denoting the respective values of  and . 

The third line contains two space-separated integers denoting the respective values of  and . 

The fourth line contains  space-separated integers denoting the respective distances that each apple falls from point . 

The fifth line contains  space-separated integers denoting the respective distances that each orange falls from point .



## 11. Valid Parentheses



Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.



An input string is valid if:



Open brackets must be closed by the same type of brackets.

Open brackets must be closed in the correct order.

Every close bracket has a corresponding open bracket of the same type.

 



### Example 1:

    Input: s = "()"

    Output: true

    

### Example 2:

    Input: s = "()[]{}"

    Output: true



### Example 3:

    Input: s = "(]"

    Output: false



## 12. Two Sum



Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.



## Example 1:

    Input: nums = [2,7,11,15], target = 9

    Output: [0,1]

    Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].



## Example 2:

    Input: nums = [3,2,4], target = 6

    Output: [1,2]



## Example 3:

    Input: nums = [3,3], target = 6

    Output: [0,1]



## 13. If Else



Given an integer, n, perform the following conditional actions:

If  is odd, print Weird

If  is even and in the inclusive range of 2 to 5, print Not Weird

If  is even and in the inclusive range of 6 to 20, print Weird

If  is even and greater than 20, print Not Weird

Input Format

A single line containing a positive integer, n.