# k-th missing element in sorted array

Given an increasing sequence a[], we need to find the K-th missing contiguous element in the increasing sequence which is not present in the sequence. If no k-th missing element is there output -1.

Examples :

```Input : a[] = {2, 3, 5, 9, 10};
k = 1;
Output : 4
Explanation: Missing Element in the increasing
sequence are {4, 6, 7, 8}. So k-th missing element
is 4

Input : a[] = {2, 3, 5, 9, 10, 11, 12};
k = 4;
Output : 8
Explanation: missing element in the increasing
sequence are {4, 6, 7, 8}  so k-th missing
element is 8
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Start iterating over the array elements, and for every element check if next element is consecutive or not, if not, then take difference between these two, and check if difference is greater than or equal to given k, then calculate ans = a[i] + count, else iterate for next element.

## C++

 `#include ` `using` `namespace` `std; ` ` `  `// Function to find k-th  ` `// missing element ` `int` `missingK(``int` `a[], ``int` `k,  ` `             ``int` `n) ` `{ ` `    ``int` `difference = 0,  ` `        ``ans = 0, count = k; ` `    ``bool` `flag = 0; ` `     `  `    ``// interating over the array ` `    ``for``(``int` `i = 0 ; i < n - 1; i++) ` `    ``{    ` `        ``difference = 0; ` `         `  `        ``// check if i-th and  ` `        ``// (i + 1)-th element  ` `        ``// are not consecutive ` `        ``if` `((a[i] + 1) != a[i + 1])  ` `        ``{ ` `             `  `            ``// save their difference ` `            ``difference +=  ` `                ``(a[i + 1] - a[i]) - 1; ` `             `  `            ``// check for difference ` `            ``// and given k ` `            ``if` `(difference >= count) ` `                ``{ ` `                    ``ans = a[i] + count; ` `                    ``flag = 1; ` `                    ``break``; ` `                ``} ` `            ``else` `                ``count -= difference; ` `        ``} ` `    ``} ` `     `  `    ``// if found ` `    ``if``(flag) ` `        ``return` `ans; ` `    ``else` `        ``return`  `-1; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``// Input array ` `    ``int` `a[] = {1, 5, 11, 19}; ` `     `  `    ``// k-th missing element  ` `    ``// to be found in the array ` `    ``int` `k = 11; ` `    ``int` `n = ``sizeof``(a) / ``sizeof``(a); ` `     `  `    ``// calling function to ` `    ``// find missing element ` `    ``int` `missing = missingK(a, k, n); ` `     `  `    ``cout << missing << endl; ` `     `  `    ``return` `0; ` `} `

## Java

 `// Java program to check for ` `// even or odd ` `import` `java.io.*; ` `import` `java.util.*; ` `  `  `public` `class` `GFG { ` `      `  `    ``// Function to find k-th  ` `    ``// missing element ` `    ``static` `int` `missingK(``int` `[]a, ``int` `k,  ` `                                 ``int` `n) ` `    ``{ ` `        ``int` `difference = ``0``,  ` `            ``ans = ``0``, count = k; ` `        ``boolean` `flag = ``false``; ` `          `  `        ``// interating over the array ` `        ``for``(``int` `i = ``0` `; i < n - ``1``; i++) ` `        ``{  ` `            ``difference = ``0``; ` `              `  `            ``// check if i-th and  ` `            ``// (i + 1)-th element  ` `            ``// are not consecutive ` `            ``if` `((a[i] + ``1``) != a[i + ``1``])  ` `            ``{ ` `                  `  `                ``// save their difference ` `                ``difference +=  ` `                    ``(a[i + ``1``] - a[i]) - ``1``; ` `                  `  `                ``// check for difference ` `                ``// and given k ` `                ``if` `(difference >= count) ` `                    ``{ ` `                        ``ans = a[i] + count; ` `                        ``flag = ``true``; ` `                        ``break``; ` `                    ``} ` `                ``else` `                    ``count -= difference; ` `            ``} ` `        ``} ` `          `  `        ``// if found ` `        ``if``(flag) ` `            ``return` `ans; ` `        ``else` `            ``return` `-``1``; ` `    ``} ` `      `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `          `  `        ``// Input array ` `        ``int` `[]a = {``1``, ``5``, ``11``, ``19``}; ` `          `  `        ``// k-th missing element  ` `        ``// to be found in the array ` `        ``int` `k = ``11``; ` `        ``int` `n = a.length; ` `          `  `        ``// calling function to ` `        ``// find missing element ` `        ``int` `missing = missingK(a, k, n); ` `          `  `        ``System.out.print(missing); ` `    ``} ` `  `  `} ` `  `  `// This code is contributed by ` `// Manish Shaw (manishshaw1) `

## Python3

 `# Function to find k-th  ` `# missing element ` `def` `missingK(a, k, n) : ` ` `  `    ``difference ``=` `0` `    ``ans ``=` `0` `    ``count ``=` `k ` `    ``flag ``=` `0` `     `  `    ``# interating over the array ` `    ``for` `i ``in` `range` `(``0``, n``-``1``) :  ` `        ``difference ``=` `0` `         `  `        ``# check if i-th and  ` `        ``# (i + 1)-th element  ` `        ``# are not consecutive ` `        ``if` `((a[i] ``+` `1``) !``=` `a[i ``+` `1``]) : ` `         `  `             `  `            ``# save their difference ` `            ``difference ``+``=` `(a[i ``+` `1``] ``-` `a[i]) ``-` `1` `             `  `            ``# check for difference ` `            ``# and given k ` `            ``if` `(difference >``=` `count) : ` `                    ``ans ``=` `a[i] ``+` `count ` `                    ``flag ``=` `1` `                    ``break` `            ``else` `: ` `                ``count ``-``=` `difference      ` `     `  `    ``# if found ` `    ``if``(flag) : ` `        ``return` `ans ` `    ``else` `: ` `        ``return` `-``1` ` `  `# Driver code ` `# Input array ` `a ``=` `[``1``, ``5``, ``11``, ``19``] ` ` `  `# k-th missing element  ` `# to be found in the array ` `k ``=` `11` `n ``=` `len``(a) ` ` `  `# calling function to ` `# find missing element ` `missing ``=` `missingK(a, k, n) ` ` `  `print``(missing) ` ` `  `# This code is contributed by  ` `# Manish Shaw (manishshaw1) `

## C#

 `// C# program to check for ` `// even or odd ` `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG { ` `     `  `    ``// Function to find k-th  ` `    ``// missing element ` `    ``static` `int` `missingK(``int` `[]a, ``int` `k,  ` `                                 ``int` `n) ` `    ``{ ` `        ``int` `difference = 0,  ` `            ``ans = 0, count = k; ` `        ``bool` `flag = ``false``; ` `         `  `        ``// interating over the array ` `        ``for``(``int` `i = 0 ; i < n - 1; i++) ` `        ``{  ` `            ``difference = 0; ` `             `  `            ``// check if i-th and  ` `            ``// (i + 1)-th element  ` `            ``// are not consecutive ` `            ``if` `((a[i] + 1) != a[i + 1])  ` `            ``{ ` `                 `  `                ``// save their difference ` `                ``difference +=  ` `                    ``(a[i + 1] - a[i]) - 1; ` `                 `  `                ``// check for difference ` `                ``// and given k ` `                ``if` `(difference >= count) ` `                    ``{ ` `                        ``ans = a[i] + count; ` `                        ``flag = ``true``; ` `                        ``break``; ` `                    ``} ` `                ``else` `                    ``count -= difference; ` `            ``} ` `        ``} ` `         `  `        ``// if found ` `        ``if``(flag) ` `            ``return` `ans; ` `        ``else` `            ``return` `-1; ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `         `  `        ``// Input array ` `        ``int` `[]a = {1, 5, 11, 19}; ` `         `  `        ``// k-th missing element  ` `        ``// to be found in the array ` `        ``int` `k = 11; ` `        ``int` `n = a.Length; ` `         `  `        ``// calling function to ` `        ``// find missing element ` `        ``int` `missing = missingK(a, k, n); ` `         `  `        ``Console.Write(missing); ` `    ``} ` ` `  `} ` ` `  `// This code is contributed by ` `// Manish Shaw (manishshaw1) `

## PHP

 `= ``\$count``) ` `                ``{ ` `                    ``\$ans` `= ``\$a``[``\$i``] + ``\$count``; ` `                    ``\$flag` `= 1; ` `                    ``break``; ` `                ``} ` `            ``else` `                ``\$count` `-= ``\$difference``; ` `        ``} ` `    ``} ` `     `  `    ``// if found ` `    ``if``(``\$flag``) ` `        ``return` `\$ans``; ` `    ``else` `        ``return` `-1; ` `} ` ` `  `// Driver Code ` ` `  `// Input array ` `\$a` `= ``array``(1, 5, 11, 19); ` ` `  `// k-th missing element  ` `// to be found in the array ` `\$k` `= 11; ` `\$n` `= ``count``(``\$a``); ` ` `  `// calling function to ` `// find missing element ` `\$missing` `= missingK(``\$a``, ``\$k``, ``\$n``); ` ` `  `echo` `\$missing``; ` ` `  `// This code is contributed by Manish Shaw ` `// (manishshaw1) ` `?> `

Output :

```14
```

Time Complexity :O(n), where n is the number of elements in the array.

My Personal Notes arrow_drop_up Sometimes you never realize the value of a moment until it becomes a memory

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Improved By : manishshaw1

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