What is Functional Interface?
A functional interface is any interface which contains only one abstract method. A functional interface can have one or more default and static methods.
Also, there is an annotation in Java @FunctionalInterface which is used to annotate the functional interfaces. It is not a mandate for functional interfaces to carry this annotation.
There are many predefined functional interfaces in Java which belong to the package java.util.function
What is the significance of these interfaces?
These interfaces as we know declare a method which can be implemented and us...

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# Author: dharam

## Understanding Binary Search Algorithm

Introduction
The problem of searching is very trivial. It goes like this:
There is an array of elements A[1..N] and we need to find the index of a given element in the array. In case the element is not present in the array, we can choose to return a specific value (say -1) which suggests that the element doesn't exist in the array.
Binary Search is a very efficient and interesting searching algorithm. Regular searching algorithms take running time proportional to the size of the input. They are called linear time algorithm O(N) to be asymptotically true.
Binary Search on the other ha...

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## Introduction to Lambda Expressions – Java8

What are Lambda Expressions?
Lambda expressions are another way of writing inline unnamed code block which performs a simple function. Not a direct analogy but if you recall anonymous classes in Java they are a way of writing inline classes. On similar lines Lambda expressions are a way to write method body inline.
They can be considered as anonymous methods, there is no need to formally define these methods but the code in the lambda expression is the body of the method.
Lambda Expression Example
If I want to write a print method which prints the content of a List of strings which is pa...

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## Finding Missing Number in an Increasing Sequence

Problem Statement
You are given an array which contains an increasing sequence of numbers from 1 to N. There is one number missing in the sequence. The task at hand is find the missing number in minimum running time.
Input: An array A of numbers in increasing order, with one number missing.
Output: The missing integer
Constraint: The sequence is strictly increasing. The algorithm should finish in minimum time.
Approach for Finding Missing Number
At first, it looks like a simple problem which can be solved in O(N) time. Indeed it is. Here are the steps:
Start traversing from the...

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## Data Structure for Efficient Search

Problem Statement
Given one million 10 digit unique integers, design an efficient data structure which has lowest time complexity for searches. You are given ample amount of space and the time for building the data structure and populating it is not judged.
The only criteria is to offer efficient searches.
Thought Process for Efficient Search
The numbers are 10 digit unique integers and we need a data structure which can offer search in near constant time. The problem is similar to finding if a word exists in a dictionary. Its just that the Strings are replaced by the 10 digit numbers.
...

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