Find a pair of numbers from an array whose sum equals k

Objective: Write an algorithm to find out whether in a given array there exists or not two numbers whose sum is exactly equals to a given number. This problem has been asked in Amazon and Microsoft interviews.

Input: An array arrA[], A number k

Output: True or false based upon we have found any two numbers in array arrA[] whose sum is equal to k

Approach:

Method 1: Using Binary Search

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Check If String has All Unique Characters

Objective: Write an algorithm to find out whether in a given string contains all the unique characters. This question has been asked in the Amazon and Microsoft interviews.

Input:  A String

Output: True or false based upon whether string contains all the unique characters or not.

Approach:

Method 1.

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Valid or Well Formed Parentheses | Part – 1

Objective: You have been asked to Write an algorithm to find Whether Given the Sequence of parentheses are well formed. This question was asked in the Amazon Interview.

Input: A String contains a sequence of parentheses

Output: true or false on whether parentheses are well formed or not

Approach:

  • Idea is to have two counters, one for open parentheses ‘{‘ and one for close ‘}’
  • Read one character at a time and increment one of the counters
  • If any given point of time count of close parentheses is greater than the open one, return false
  • If at the end both counters are equal, return true

Example: { { } { } } – Well formed

{ { } { = Not well formed

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Find an Element in 2 dimensional sorted array

Objective : Write an algorithm to find an Element in 2 dimensional array where rows and columns are sorted respectively.

Input: A two dimensional sorted array, arrA[][].

Sorted 2D array

 

Output : True or false based on whether element exists and its location

Approach:

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