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Add 1 to a given number
• Difficulty Level : Medium
• Last Updated : 26 Apr, 2021

Write a program to add one to a given number. The use of operators like ‘+’, ‘-‘, ‘*’, ‘/’, ‘++’, ‘–‘ …etc are not allowed.
Examples:

```Input:  12
Output: 13

Input:  6
Output: 7```

This question can be approached by using some bit magic. Following are different methods to achieve the same using bitwise operators.
Method 1
To add 1 to a number x (say 0011000111), flip all the bits after the rightmost 0 bit (we get 0011000000). Finally, flip the rightmost 0 bit also (we get 0011001000) to get the answer.

## C++

 `// C++ code to add add``// one to a given number``#include ``using` `namespace` `std;` `int` `addOne(``int` `x)``{``    ``int` `m = 1;``    ` `    ``// Flip all the set bits``    ``// until we find a 0``    ``while``( x & m )``    ``{``        ``x = x ^ m;``        ``m <<= 1;``    ``}``    ` `    ``// flip the rightmost 0 bit``    ``x = x ^ m;``    ``return` `x;``}` `/* Driver program to test above functions*/``int` `main()``{``    ``cout<

## C

 `// C++ code to add add``// one to a given number``#include ` `int` `addOne(``int` `x)``{``    ``int` `m = 1;``    ` `    ``// Flip all the set bits``    ``// until we find a 0``    ``while``( x & m )``    ``{``        ``x = x ^ m;``        ``m <<= 1;``    ``}``    ` `    ``// flip the rightmost 0 bit``    ``x = x ^ m;``    ``return` `x;``}` `/* Driver program to test above functions*/``int` `main()``{``    ``printf``(``"%d"``, addOne(13));``    ``getchar``();``    ``return` `0;``}`

## Java

 `// Java code to add add``// one to a given number``class` `GFG {` `    ``static` `int` `addOne(``int` `x)``    ``{``        ``int` `m = ``1``;``        ` `        ``// Flip all the set bits``        ``// until we find a 0``        ``while``( (``int``)(x & m) >= ``1``)``        ``{``            ``x = x ^ m;``            ``m <<= ``1``;``        ``}``    ` `        ``// flip the rightmost 0 bit``        ``x = x ^ m;``        ``return` `x;``    ``}``    ` `    ``/* Driver program to test above functions*/``    ``public` `static` `void` `main(String[] args)``    ``{``        ``System.out.println(addOne(``13``));``    ``}``}` `// This code is contributed by prerna saini.`

## Python3

 `# Python3 code to add 1``# one to a given number``def` `addOne(x) :``    ` `    ``m ``=` `1``;``    ``# Flip all the set bits``    ``# until we find a 0``    ``while``(x & m):``        ``x ``=` `x ^ m``        ``m <<``=` `1``    ` `    ``# flip the rightmost``    ``# 0 bit``    ``x ``=` `x ^ m``    ``return` `x` `# Driver program``n ``=` `13``print` `addOne(n)` `# This code is contributed by Prerna Saini.`

## C#

 `// C# code to add one``// to a given number``using` `System;` `class` `GFG {` `    ``static` `int` `addOne(``int` `x)``    ``{``        ``int` `m = 1;``        ` `        ``// Flip all the set bits``        ``// until we find a 0``        ``while``( (``int``)(x & m) == 1)``        ``{``            ``x = x ^ m;``            ``m <<= 1;``        ``}``    ` `        ``// flip the rightmost 0 bit``        ``x = x ^ m;``        ``return` `x;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `Main()``    ``{``        ``Console.WriteLine(addOne(13));``    ``}``}` `// This code is contributed by vt_m.`

## PHP

 ``

## Javascript

 ``

Output:

`14`

Method 2
We know that the negative number is represented in 2’s complement form on most of the architectures. We have the following lemma hold for 2’s complement representation of signed numbers.
Say, x is numerical value of a number, then
~x = -(x+1) [ ~ is for bitwise complement ]
(x + 1) is due to the addition of 1 in 2’s complement conversion
To get (x + 1) apply negation once again. So, the final expression becomes (-(~x)).

## C++

 `#include ``using` `namespace` `std;` `int` `addOne(``int` `x)``{``    ``return` `(-(~x));``}` `/* Driver code*/``int` `main()``{``    ``cout<

## C

 `#include` `int` `addOne(``int` `x)``{``   ``return` `(-(~x));``}` `/* Driver program to test above functions*/``int` `main()``{``  ``printf``(``"%d"``, addOne(13));``  ``getchar``();``  ``return` `0;``}`

## Java

 `// Java code to Add 1 to a given number``class` `GFG``{``    ``static` `int` `addOne(``int` `x)``    ``{``         ``return` `(-(~x));``    ``}``    ` `    ``// Driver program``    ``public` `static` `void` `main(String[] args)``    ``{``        ``System.out.printf(``"%d"``, addOne(``13``));``    ``}``}` `// This code is contributed``// by Smitha Dinesh Semwal`

## Python3

 `# Python3 code to add 1 to a given number` `def` `addOne(x):``    ``return` `(``-``(~x));`  `# Driver program``print``(addOne(``13``))` `# This code is contributed by Smitha Dinesh Semwal`

## C#

 `// C# code to Add 1``// to a given number``using` `System;` `class` `GFG``{``    ``static` `int` `addOne(``int` `x)``    ``{``        ``return` `(-(~x));``    ``}``    ` `    ``// Driver program``    ``public` `static` `void` `Main()``    ``{``        ``Console.WriteLine(addOne(13));``    ``}``}` `// This code is contributed by vt_m.`

## PHP

 ``

## Javascript

 ``

Output:

`14`

Example :

```Assume the machine word length is one *nibble* for simplicity.
And x = 2 (0010),
~x = ~2 = 1101 (13 numerical)
-~x = -1101```

Interpreting bits 1101 in 2’s complement form yields numerical value as -(2^4 – 13) = -3. Applying ‘-‘ on the result leaves 3. The same analogy holds for decrement. Note that this method works only if the numbers are stored in 2’s complement form.

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