Given a sorted array of size n and given that there are numbers from 1 to n+1 with one missing, the missing number is to be found. It may be assumed that array has distinct elements.**Examples:**

Input : 1 3 4 5 6 Output : 2 Input : 1 2 3 4 5 7 8 9 10 Output : 6

We traverse all elements. For every element a[i], we check if it is equal to i+1 or not. If not, we return (i+1).

## C++

`// C++ program to find missing Number in` `// a sorted array of size n and distinct` `// elements.` `#include<bits/stdc++.h>` `using` `namespace` `std;` `// Function to find missing number` `int` `getMissingNo(` `int` `a[], ` `int` `n)` `{` ` ` `for` `(` `int` `i=0; i<n; i++) ` ` ` `if` `(a[i] != (i+1))` ` ` `return` `(i+1);` ` ` ` ` `// If all numbers from 1 to n` ` ` `// are present` ` ` `return` `n+1;` `}` `// Driver code` `int` `main()` `{` ` ` `int` `a[] = {1, 2, 4, 5, 6};` ` ` `int` `n = ` `sizeof` `(a) / ` `sizeof` `(a[0]);` ` ` `cout << getMissingNo(a, n);` ` ` `return` `0;` `}` `// This code is contributed by Sachin Bisht` |

## Java

`// Java program to find missing Number in` `// a sorted array of size n and distinct` `// elements.` `class` `Main` `{` ` ` `// Function to find missing number` ` ` `static` `int` `getMissingNo(` `int` `a[])` ` ` `{` ` ` `int` `n = a.length;` ` ` `for` `(` `int` `i=` `0` `; i<n; i++) ` ` ` `if` `(a[i] != (i+` `1` `))` ` ` `return` `(i+` `1` `);` ` ` `// If all numbers from 1 to n` ` ` `// are present` ` ` `return` `n+` `1` `;` ` ` `}` ` ` ` ` `/* program to test above function */` ` ` `public` `static` `void` `main(String args[])` ` ` `{` ` ` `int` `a[] = {` `1` `, ` `2` `, ` `4` `, ` `5` `, ` `6` `};` ` ` `System.out.println(getMissingNo(a));` ` ` `}` `}` |

## Python

`# Python program to find missing Number in` `# a sorted array of size n and distinct` `# elements.` `# function to find missing number` `def` `getMissingNo(a):` ` ` `n ` `=` `len` `(a)` ` ` ` ` `for` `i ` `in` `range` `(n):` ` ` `if` `(a[i] !` `=` `i ` `+` `1` `):` ` ` `return` `i ` `+` `1` ` ` ` ` `# If all numbers from 1 to n` ` ` `# are present` ` ` `return` `n` `+` `1` `# Driver code` `a ` `=` `[` `1` `, ` `2` `, ` `4` `, ` `5` `, ` `6` `]` `print` `(getMissingNo(a))` `# This code is contributed by Sachin Bisht` |

## C#

`// C# program to find missing Number` `// in a sorted array of size n and` `// distinct elements.` `using` `System;` `class` `GFG` `{` ` ` `// Function to find missing number` `static` `int` `getMissingNo(` `int` `[]a, ` `int` `n)` `{` ` ` `for` `(` `int` `i = 0; i < n; i++)` ` ` `if` `(a[i] != (i + 1))` ` ` `return` `(i + 1);` ` ` `// If all numbers from` ` ` `// 1 to n are present` ` ` `return` `n + 1;` `}` `// Driver code` `public` `static` `void` `Main()` `{` ` ` `int` `[]a = {1, 2, 4, 5, 6};` ` ` `int` `n = a.Length;` ` ` `Console.WriteLine(getMissingNo(a, n));` `}` `}` `// This code is contributed by ihritik` |

## PHP

`<?php` `// PHP program to find missing Number` `// in a sorted array of size n and` `// distinct elements.` `// Function to find missing number` `function` `getMissingNo(` `$a` `, ` `$n` `)` `{` ` ` `for` `(` `$i` `= 0; ` `$i` `< ` `$n` `; ` `$i` `++)` ` ` `if` `(` `$a` `[` `$i` `] != (` `$i` `+ 1))` ` ` `return` `(` `$i` `+ 1);` ` ` `// If all numbers from` ` ` `// 1 to n are present` ` ` `return` `$n` `+ 1;` `}` `// Driver code` `$a` `= ` `array` `(1, 2, 4, 5, 6);` `$n` `= sizeof(` `$a` `);` `echo` `getMissingNo(` `$a` `, ` `$n` `);` `// This code is contributed` `// by ihritik` `?>` |

## Javascript

`<script>` `// javascipt program to find missing Number` `// in a sorted array of size n and` `// distinct elements.` ` ` `// Function to find missing number` `function` `getMissingNo(a,n)` `{` ` ` `for` `(let i = 0; i < n; i++)` ` ` `if` `(a[i] != (i + 1))` ` ` `return` `(i + 1);` ` ` `// If all numbers from` ` ` `// 1 to n are present` ` ` `return` `n + 1;` `}` `// Driver code` `let a = [1, 2, 4, 5, 6]` `let n = a.length;` `document.write(getMissingNo(a, n));` `// This code is contributed by mohit kumar 29.` `</script>` |

**Output :**

3

**Time Complexity: **O(n)

**Auxiliary Space: **O(1)

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