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Data Structures
  • Data Structures Manual
  • Arrays
    • Array ADT
    • Linear Search
    • Binary Search
    • Some More Basic Operations
    • Reversing an Array
    • Operations in a Sorted Array
    • Merging Two Arrays
    • Set Operations
    • Finding Missing Elements
    • Duplicates in an Array
    • Getting a Pair whose Sum = K
    • Finding Max & Min in Single Scan
  • Strings
    • Finding the Length of a String
    • Changing Cases in a String
    • Finding Number of Vowels, Consonants & Words
    • Reversing a String
    • Checking for Palindrome
    • Duplicates in a String
    • Checking if Strings are Anagrams
    • Permutations of a String
  • Singly Linked List
    • Displaying the Nodes
    • Counting the Nodes
    • Sum of all Nodes
    • Finding the Maximum Element
    • Searching in a Node
    • Inserting a Node
    • Inserting a Node in Sorted List
    • Deleting a Node
    • Checking if List is Sorted
    • Removing Duplicates from a List
    • Reversing a Linked List
    • Concatenating Two Lists
    • Detecting a Loop in Linked List
    • Merge Two Sorted Lists
    • Finding the Middle Node
  • Cirular Linked List
    • Displaying the Nodes
    • Inserting a Node
    • Deleting a Node
  • Doubly Linked List
    • Inserting a Node
    • Deleting a Node
    • Reversing a Doubly Linked List
    • Circular Doubly Linked List
  • Stack
    • Stack Using Array
    • Stack Using Linked List
    • Balancing Parenthesis
    • Infix to Postfix
    • Evaluation of Postfix Expression
  • Queue
    • Queue using Array
    • Queue using Linked List
    • Double Ended Queue
  • Binary Tree
    • Creating a Binary Tree using Queue
    • Recursive Tree Traversals
    • Iterative Tree Traversals
    • Level Order Traversal
    • Counting Nodes in a Binary Tree
    • Finding the Height of Tree
    • Finding Sum of All Nodes
  • Binary Search Tree
    • Searching in a BST
    • Inserting in a BST
    • Deleting in a BST
  • AVL Tree
    • Inserting in an AVL Tree
    • AVL Tree Rotations
    • Deleting in an AVL Tree
  • Heap
    • Inserting in a Heap
    • Deleting in a Heap
    • Heapify
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  • Single Element Missing :
  • Multiple Elements Missing :
  • Using Hash Array :

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  1. Arrays

Finding Missing Elements

Methods to find one or more missing elements in an array.

Single Element Missing :

void findMissing(int a[], int n, int start) {

    int difference = start - 0;
    
    for (int i = 0; i < n; i++) {
        if (a[i] - i != difference) {
            printf("Missing Element : %d\n", i + difference);
            break;
        }
    }

}

Multiple Elements Missing :

void findMissing(int a[], int n, int start) {

    int diff = start - 0;
    printf("Missing Elements :\n");
    
    for (int i = 0; i < n; i++) {
        if (a[i] - i != diff) {
            while (diff < a[i] - i) {
                printf("%d\t", i + diff);
                diff++;
            }
        }
    }

}

Using Hash Array :

void findMissing(int a[], int n, int high) {

    // Creating and initializing hash array with 0
    // Size of hash array = maximum element in input array
    int h[high];
    for (int i = 0; i < high; i++) {
        h[i] = 0;
    }
    
    // Incrementing hash table values as per the numbers in
    // original input array
    for (int i = 0; i < n; i++) {
        h[a[i]]++;
    }
    
    printf("Missing Elements :\n");
    for (int i = low; i <= high; i++) {
        if (h[i] == 0) {
            printf("%d\t", i);
        }
    }

}

Contributed by Nitin Ranganath

PreviousSet OperationsNextDuplicates in an Array

Last updated 4 years ago

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