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## 9. Which sorting algorithm is the fastest
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Solution: There are many types of sorting algorithms: quick sort, bubble sort, balloon sort, radix sort, merge sort, etc. Not one can be considered the fastest because each algorithm is designed for a particular data structure and data set. It would depend on the data set that you would want to sort.
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## Some common algorithm problems asked at online tests :
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### 10. Save all leaf nodes of a Binary tree in a Doubly Linked List by using Right node as Next node and Left Node as Previous Node.
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### 11. Given an array,find the maximum j – i such that arr[j] > arr[i]
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### 12. Remove Alternate Duplicate characters from a char array you have to do it in Place.Like keeping only the odd occurences of each character.
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`Example: Input: "you got beautiful eyes"
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Output: "you gtbeaiful es"`
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Allowed Time Complexity was O(n) and Space Complexity was O(1)
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### 13. In a file there are 1 million words . Find 10 most frequent words in that file.
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### 14. Find all nodes at k-distance from a given node in a binary tree
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### 15. Clone a linked list with next and random pointer
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### 16. Serialise and Deserialise a linked list with next and random pointer.
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### 17. Construct a binary tree from given inorder and preorder traversals.
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### 18. Return a tree such that each internal node stores sum of all its child nodes. Each leaf node stores zero.
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### 20. How will you implement linked list with 1 million nodes? How will you access 999999 th node? Give some optimal design strategy and implementation.
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### 21. Reversal of Linked List in groups of K.
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### 22. Given a positive integer N, count all possible distinct binary strings of length N such that there are no consecutive 1’s.
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### 23. Check whether given binary tree is balanced or not. Definition was no two leaves should have height difference of greater than one.
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### 24. Remove duplicates from string in place in O(n).
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### 25. Connect nodes on same level in a binary tree.
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### 26. Find sum of data of all leaves of a binary tree on same level and then multiply sums obtained of all levels.
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### 27. Given a matrix of characters and a word. You have to count the number of occurrences of that word in that matrix. you can move to any of the eight valid directions from current position.
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### 28. You are given an string as input which represents a path. You have to normalize that path inplace(NO EXTRA SPACE).
### 29. Least common ancestor of two nodes in a binary tree
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### 30. Given two sorted arrays (with repetitive elements) find the kth minimum number from both arrays.
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### 31. Given the root to a binary tree, a value n and k.Find the sum of nodes at distance k from node with value n
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### 32. Find an element in a rotated array. The cost of a stock on each day is given in an array, find the max profit that you can make by buying and selling in those days.
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`For example, if the given array is {100, 180, 260, 310, 40, 535, 695},
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the maximum profit can earned by buying on day 0, selling on day 3.
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Again buy on day 4 and sell on day 6.
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If the given array of prices is sorted in decreasing order, then profit cannot be earned at all.`
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### 32. Given two linked lists both represent a number. Create a linked list that contains its sum.
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### 33. Given a binary search tree , print the path which has the sum equal to k and has minimum hops. i.e if there are multiple paths with the sum equal to k then print the path with minimum number of nodes.
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### 34. A MxN matrix containing integers (positive, negative and zero’s). For every position containing 0, mark the corresponding row and column as 0. Rotate MxN matrix by 90 degress.
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### 35. Find the nth number that contains the digit k or is divisible by k. (2 <= k <= 9)
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### 36. Write a program to connect next left node in a binary tree. Also first node of each level should be pointing to last node of next level? (Without using Queue)
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### 37. Convert a binary tree to its sum tree(each node is the sum of its children)
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### 38. Given a directed graph. Construct another graph from given graph such that if path exists from vertices A to vertices B and from B to C, then path from A to C and from C to A also should exists.
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### 39. Implement hashmap on your own. Write good hashing function for string.
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### 40. Given an array, arrange the elements such that the number formed by concatenating the elements is highest.
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`E.g.: input = [9, 93, 24, 6],
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the output should be: [9,93,6,24].
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This is because if you concatenate all the numbers,
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993624 is the highest number that can be formed.`
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#### 41. Given a string, find the longest substring which is palindrome.
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#### 42. Given that integers are read from a data stream. Find median of elements read so for in efficient way. For simplicity assume there are no duplicates.
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#### 43. Write an efficient program for printing k largest elements in an array. Elements in array can be in any order.
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#### 44. Given unsorted array and a number K. Find 2 numbers such that sum is K.
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#### 45. Given n-ary tree. zigzag level order traversal.
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#### 46. Given string s and string t find whether all permutation of t is present as substring in s.
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#### 47. Design a stack which holds an integer value such that getMinimum() function should return the minimum element in the stack. Implement popMin() function which would pop minimum element from the original stack.
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#### 48. Given a set of intervals like 5-10, 15-20, 25-40, 30-45, 50-100. Find the ith smallest number in these intervals. Assume there are no duplicate numbers.
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`e.g: 1st smallest number = 5 6th smallest number = 10
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7th smallest number = 15 and so on.`
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#### 49. Given an array which is first strictly increasing and then strictly decreasing. Find an element in this array.
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Given a string example : shoppingwithflipkartiseasy, Now we are given this string and a dictionary containing valid words , now we need to break the sentence into words separated by space. Output : shopping with flipkart is easy
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Given a series 2,3,4,5,6,8,9,10,......, here in this series all the numbers are present which have factors only and only either 2,3 or 5. Need to write a node to generate nth number for the series . With best approach and complexity
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Given a tree with edge weights, find any path in the tree with maximum sum of edges.
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Merge k sorted arrays.
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Given a maze, a start point and end point find the shortest path to reach the end point from the starting point.
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Given a sentence and a set of characters. Find the minimum window within which the set of characters can be found in the sentence in any order.
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You are given a string of 0’s and 1’s you have to find the number of substrings in the string which starts and end with a 1.
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eg : input : 0010110010 output : 6
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You are given a mapping like a -> 1, b-> 2... z-> 26. You have to print all possible combinations of a given number using the above information.
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eg : input : 121 output : aba,la,au
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Given a dictionary of 50,000 words. Given a phrase without spaces, add spaces to make it a proper sentence.
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e.g:input: thequickbrownfoxjumpoverlazydog
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output: the quick brown fox jump over lazy dog
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Given an unsorted array of n integers which can contain integers from 1 to n. Some elements can be repeated multiple times and some other elements can be absent from the array. Count frequency of all elements that are present and print the missing elements.
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Examples:Input: arr[] = {2, 3, 3, 2, 5}
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Output: Below are frequencies of all elements
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1 -> 0 2 -> 2 3 -> 2 4 -> 0 5 -> 1
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Get the next bigger number using the same digits of a number.
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Eg, For 123456, next number would be 123465
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Given a boolean 2D matrix, find the number of islands. A group of connected 1s forms an island. For example, the below matrix contains 5 islands
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Input : mat[][] =
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{{1, 1, 0, 0, 0},
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{0, 1, 0, 0, 1},
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{1, 0, 0, 1, 1},
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{0, 0, 0, 0, 0},
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{1, 0, 1, 0, 1}}
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Output : 5
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Given two strings in lowercase, the task is to make them anagram. The only allowed operation is to remove a character from any string. Find minimum number of characters to be deleted to make both the strings anagram?
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If two strings contains same data set in any order then strings are called Anagrams.
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Examples:
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Input : str1 = "bcadeh" str2 = "hea"
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Output: 3
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We need to remove b, c and d from str1.
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Input : str1 = "cddgk" str2 = "gcd"
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Output: 2
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Input : str1 = "bca" str2 = "acb"
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Output: 0
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Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.
Trap "1 unit" between first 1 and 2, "4 units" between
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first 2 and 3 and "1 unit" between second last 1 and last 2
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Given two strings str1 and str2 and below operations that can performed on str1. Find minimum number of edits (operations) required to convert ‘str1’ into ‘str2’.
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Insert
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Remove
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Replace
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All of the above operations are of equal cost.
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Examples:
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Input: str1 = "geek", str2 = "gesek"
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Output: 1
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We can convert str1 into str2 by inserting a 's'.
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Input: str1 = "cat", str2 = "cut"
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Output: 1
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We can convert str1 into str2 by replacing 'a' with 'u'.
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Input: str1 = "sunday", str2 = "saturday"
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Output: 3
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Last three and first characters are same. We basically
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need to convert "un" to "atur". This can be done using
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below three operations.
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Replace 'n' with 'r', insert t, insert a
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Given a string with repeated characters, task is rearrange characters in a string so that no two adjacent characters are same.
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Note : It may be assumed that the string has only lowercase English alphabets.
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Examples:
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Input: aaabc
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Output: abaca
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Input: aaabb
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Output: ababa
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Input: aa
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Output: Not Possible
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Input: aaaabc
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Output: Not Possible
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This problem is know as Clock angle problem where we need to find angle between hands of an analog clock at a given time.
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Examples:Input: h = 12:00, m = 30.00
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Output: 165 degreeInput: h = 3.00, m = 30.00 Output: 75 degree
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