# Find the smallest positive number missing from an unsorted array | Set 3

Given an unsorted array with both positive and negative elements. The task is to find the smallest positive number missing from the array.

Examples:

Input: arr[] = {2, 3, 7, 6, 8, -1, -10, 15}
Output: 1

Input: arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 }
Output: 4

Input: arr[] = {1, 1, 0, -1, -2}
Output: 2

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

Approach :
We have already discussed some of the techniques to find the smallest positive number missing from an unsorted array.

Here, we use set to store all positive integers and find the first missing positive integer.

## C++

 `// CPP program to find the smallest ` `// positive missing number ` `#include ` `using` `namespace` `std; ` ` `  `// Function to find the smallest ` `// positive missing number ` `int` `findMissingPositive(``int` `arr[], ``int` `n) ` `{ ` `    ``// Default smallest Positive Integer ` `    ``int` `m = 1; ` ` `  `    ``// Store values in set which are ` `    ``// greater than variable m ` `    ``set<``int``> x; ` ` `  `    ``for` `(``int` `i = 0; i < n; i++) { ` `        ``// Store value when m is less than ` `        ``// current index of given array ` `        ``if` `(m < arr[i]) { ` `            ``x.insert(arr[i]); ` `        ``} ` `        ``else` `if` `(m == arr[i]) { ` `            ``// Increment m when it is equal ` `            ``// to current element ` `            ``m = m + 1; ` ` `  `            ``while` `(x.count(m)) { ` `                ``x.erase(m); ` ` `  `                ``// Increment m when it is one of the ` `                ``// element of the set ` `                ``m = m + 1; ` `            ``} ` `        ``} ` `    ``} ` ` `  `    ``// Return the required answer ` `    ``return` `m; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 }; ` ` `  `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr); ` ` `  `    ``// Function call ` `    ``cout << findMissingPositive(arr, n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to find the smallest ` `// positive missing number ` `import` `java.util.*; ` ` `  `class` `GFG ` `{ ` ` `  `// Function to find the smallest ` `// positive missing number ` `static` `int` `findMissingPositive(``int` `arr[], ``int` `n) ` `{ ` `    ``// Default smallest Positive Integer ` `    ``int` `m = ``1``; ` ` `  `    ``// Store values in set which are ` `    ``// greater than variable m ` `    ``HashSet x = ``new` `HashSet(); ` ` `  `    ``for` `(``int` `i = ``0``; i < n; i++) ` `    ``{ ` `        ``// Store value when m is less than ` `        ``// current index of given array ` `        ``if` `(m < arr[i]) ` `        ``{ ` `            ``x.add(arr[i]); ` `        ``} ` `        ``else` `if` `(m == arr[i]) ` `        ``{ ` `            ``// Increment m when it is equal ` `            ``// to current element ` `            ``m = m + ``1``; ` ` `  `            ``while` `(x.contains(m))  ` `            ``{ ` `                ``x.remove(m); ` ` `  `                ``// Increment m when it is one of the ` `                ``// element of the set ` `                ``m = m + ``1``; ` `            ``} ` `        ``} ` `    ``} ` ` `  `    ``// Return the required answer ` `    ``return` `m; ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String[] args)  ` `{ ` `    ``int` `arr[] = { ``2``, ``3``, -``7``, ``6``, ``8``, ``1``, -``10``, ``15` `}; ` ` `  `    ``int` `n = arr.length; ` ` `  `    ``// Function call ` `    ``System.out.println(findMissingPositive(arr, n)); ` `} ` `} ` ` `  `// This code is contributed by 29AjayKumar `

## Python3

 `# Python 3 program to find the smallest ` `# positive missing number ` ` `  `# Function to find the smallest ` `# positive missing number ` `def` `findMissingPositive(arr, n): ` `     `  `    ``# Default smallest Positive Integer ` `    ``m ``=` `1` ` `  `    ``# Store values in set which are ` `    ``# greater than variable m ` `    ``x ``=` `[] ` `    ``for` `i ``in` `range``(n): ` `         `  `        ``# Store value when m is less than ` `        ``# current index of given array ` `        ``if` `(m < arr[i]): ` `            ``x.append(arr[i]) ` `     `  `        ``elif` `(m ``=``=` `arr[i]): ` `             `  `            ``# Increment m when it is equal ` `            ``# to current element ` `            ``m ``=` `m ``+` `1` ` `  `            ``while` `(x.count(m)): ` `                ``x.remove(m) ` ` `  `                ``# Increment m when it is one of the ` `                ``# element of the set ` `                ``m ``=` `m ``+` `1` ` `  `    ``# Return the required answer ` `    ``return` `m ` ` `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``arr ``=` `[``2``, ``3``, ``-``7``, ``6``, ``8``, ``1``, ``-``10``, ``15``] ` ` `  `    ``n ``=` `len``(arr) ` ` `  `    ``# Function call ` `    ``print``(findMissingPositive(arr, n)) ` ` `  `# This code is contributed by ` `# Surendra_Gangwar `

## C#

 `// C# program to find the smallest ` `// positive missing number ` `using` `System; ` `using` `System.Collections.Generic; ` `     `  `class` `GFG ` `{ ` ` `  `// Function to find the smallest ` `// positive missing number ` `static` `int` `findMissingPositive(``int` `[]arr, ``int` `n) ` `{ ` `    ``// Default smallest Positive Integer ` `    ``int` `m = 1; ` ` `  `    ``// Store values in set which are ` `    ``// greater than variable m ` `    ``HashSet<``int``> x = ``new` `HashSet<``int``>(); ` ` `  `    ``for` `(``int` `i = 0; i < n; i++) ` `    ``{ ` `        ``// Store value when m is less than ` `        ``// current index of given array ` `        ``if` `(m < arr[i]) ` `        ``{ ` `            ``x.Add(arr[i]); ` `        ``} ` `         `  `        ``else` `if` `(m == arr[i]) ` `        ``{ ` `            ``// Increment m when it is equal ` `            ``// to current element ` `            ``m = m + 1; ` ` `  `            ``while` `(x.Contains(m))  ` `            ``{ ` `                ``x.Remove(m); ` ` `  `                ``// Increment m when it is one of the ` `                ``// element of the set ` `                ``m = m + 1; ` `            ``} ` `        ``} ` `    ``} ` ` `  `    ``// Return the required answer ` `    ``return` `m; ` `} ` ` `  `// Driver code ` `public` `static` `void` `Main(String[] args)  ` `{ ` `    ``int` `[]arr = { 2, 3, -7, 6, 8, 1, -10, 15 }; ` ` `  `    ``int` `n = arr.Length; ` ` `  `    ``// Function call ` `    ``Console.WriteLine(findMissingPositive(arr, n)); ` `} ` `} ` ` `  `// This code is contributed by Rajput-Ji `

Output:

```4
```

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