# Check if a number has bits in alternate pattern | Set-2 O(1) Approach

Given a positive integer **n**. The problem is to check whether this integer has an alternate pattern in its binary representation or not. Here alternate pattern means that the set and unset bits in **n** occur in alternate order. For example- 5 has an alternate pattern i.e. 101.

Print “Yes” if it has an alternate pattern otherwise “No”. **Note:** 0 < n.**Examples :**

Input : 10 Output : Yes(10)= (1010)_{10}_{2}, has an alternate pattern. Input : 12 Output : No(12)= (1100)_{10}_{2}, does not have an alternate pattern.

**Simple Approach:** It has been discussed in this post having a time complexity of O(n).**Efficient Approach:** Following are the steps:

- Calculate
**num**= n ^ (n >> 1). If**n**has an alternate pattern, then**n ^ (n >> 1)**operation will produce a number having set bits only.**‘^’**is a bitwise XOR operation. - Check whether all the bits in
**num**are set or not. Refer this post.

## C++

`// C++ implementation to check if a number` `// has bits in alternate pattern` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// function to check if all the bits are set or not` `// in the binary representation of 'n'` `bool` `allBitsAreSet(unsigned ` `int` `n)` `{` ` ` `// if true, then all bits are set` ` ` `if` `(((n + 1) & n) == 0)` ` ` `return` `true` `;` ` ` ` ` `// else all bits are not set` ` ` `return` `false` `;` `}` `// function to check if a number` `// has bits in alternate pattern` `bool` `bitsAreInAltOrder(unsigned ` `int` `n)` `{` ` ` `unsigned ` `int` `num = n ^ (n >> 1);` ` ` ` ` `// to check if all bits are set` ` ` `// in 'num'` ` ` `return` `allBitsAreSet(num); ` `}` `// Driver program to test above` `int` `main()` `{` ` ` `unsigned ` `int` `n = 10;` ` ` ` ` `if` `(bitsAreInAltOrder(n))` ` ` `cout << ` `"Yes"` `;` ` ` `else` ` ` `cout << ` `"No"` `;` ` ` ` ` `return` `0; ` `}` |

## Java

`// Java implementation to check if a` `// number has bits in alternate pattern` `class` `AlternateSetBits` `{` ` ` `// function to check if all the bits` ` ` `// are set or not in the binary` ` ` `// representation of 'n'` ` ` `static` `boolean` `allBitsAreSet(` `int` `n)` ` ` `{` ` ` `// if true, then all bits are set` ` ` `if` `(((n + ` `1` `) & n) == ` `0` `)` ` ` `return` `true` `;` ` ` ` ` `// else all bits are not set` ` ` `return` `false` `;` ` ` `}` ` ` ` ` `// function to check if a number` ` ` `// has bits in alternate pattern` ` ` `static` `boolean` `bitsAreInAltOrder(` `int` `n)` ` ` `{` ` ` `int` `num = n ^ (n >>> ` `1` `);` ` ` ` ` `// to check if all bits are set` ` ` `// in 'num'` ` ` `return` `allBitsAreSet(num); ` ` ` `}` ` ` ` ` `// Driver Code` ` ` `public` `static` `void` `main(String args[])` ` ` `{` ` ` `int` `n = ` `10` `;` ` ` ` ` `if` `(bitsAreInAltOrder(n))` ` ` `System.out.println(` `"Yes"` `);` ` ` `else` ` ` `System.out.println(` `"No"` `);` ` ` `}` `}` `/* This code is contributed by Danish Kaleem */` |

## Python3

`# Python implementation to check if a number` `# has bits in alternate pattern` `# function to check if all the bits are set or not` `# in the binary representation of 'n'` `def` `allBitsAreSet(n):` ` ` ` ` `# if true, then all bits are set` ` ` `if` `(((n ` `+` `1` `) & n) ` `=` `=` `0` `):` ` ` `return` `True` `;` ` ` ` ` `# else all bits are not set` ` ` `return` `False` `;` `# function to check if a number` `# has bits in alternate pattern` `def` `bitsAreInAltOrder(n):` ` ` `num ` `=` `n ^ (n >> ` `1` `);` ` ` ` ` `# to check if all bits are set` ` ` `# in 'num'` ` ` `return` `allBitsAreSet(num); ` `# Driver code` `n ` `=` `10` `;` `if` `(bitsAreInAltOrder(n)):` ` ` `print` `(` `"Yes"` `);` `else` `:` ` ` `print` `(` `"No"` `);` `# This code is contributed by PrinciRaj1992` |

## C#

`// C# implementation to check if a` `// number has bits in alternate pattern` `using` `System;` `class` `GFG {` ` ` `// function to check if all the bits` ` ` `// are set or not in the binary` ` ` `// representation of 'n'` ` ` `static` `bool` `allBitsAreSet(` `int` `n)` ` ` `{` ` ` `// if true, then all bits are set` ` ` `if` `(((n + 1) & n) == 0)` ` ` `return` `true` `;` ` ` `// else all bits are not set` ` ` `return` `false` `;` ` ` `}` ` ` `// function to check if a number` ` ` `// has bits in alternate pattern` ` ` `static` `bool` `bitsAreInAltOrder(` `int` `n)` ` ` `{` ` ` `int` `num = n ^ (n >> 1);` ` ` `// to check if all bits are set` ` ` `// in 'num'` ` ` `return` `allBitsAreSet(num);` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `Main()` ` ` `{` ` ` `int` `n = 10;` ` ` `if` `(bitsAreInAltOrder(n))` ` ` `Console.WriteLine(` `"Yes"` `);` ` ` `else` ` ` `Console.WriteLine(` `"No"` `);` ` ` `}` `}` `// This code is contributed by Sam007` |

## PHP

`<?php` `// PHP implementation to check` `// if a number has bits in` `// alternate pattern` `// function to check if all the` `// bits are set or not in the` `// binary representation of 'n'` `function` `allBitsAreSet(` `$n` `)` `{` ` ` `// if true, then all` ` ` `// bits are set` ` ` `if` `(((` `$n` `+ 1) & ` `$n` `) == 0)` ` ` `return` `true;` ` ` ` ` `// else all bits are not set` ` ` `return` `false;` `}` `// function to check if a number` `// has bits in alternate pattern` `function` `bitsAreInAltOrder(` `$n` `)` `{` ` ` `$num` `= ` `$n` `^ (` `$n` `>> 1);` ` ` ` ` `// to check if all bits` ` ` `// are set in 'num'` ` ` `return` `allBitsAreSet(` `$num` `);` `}` `// Driver Code` `$n` `= 10;` `if` `(bitsAreInAltOrder(` `$n` `))` ` ` `echo` `"Yes"` `;` `else` ` ` `echo` `"No"` `;` ` ` `// This code is contributed by aj_36` `?>` |

## Javascript

`<script>` `// Javascript implementation to check if a` `// number has bits in alternate pattern` ` ` `// function to check if all the bits` ` ` `// are set or not in the binary` ` ` `// representation of 'n'` ` ` `function` `allBitsAreSet(n)` ` ` `{` ` ` `// if true, then all bits are set` ` ` `if` `(((n + 1) & n) == 0)` ` ` `return` `true` `;` ` ` ` ` `// else all bits are not set` ` ` `return` `false` `;` ` ` `}` ` ` ` ` `// function to check if a number` ` ` `// has bits in alternate pattern` ` ` `function` `bitsAreInAltOrder(n)` ` ` `{` ` ` `let num = n ^ (n >>> 1);` ` ` ` ` `// to check if all bits are set` ` ` `// in 'num'` ` ` `return` `allBitsAreSet(num); ` ` ` `}` ` ` `// driver function` ` ` `let n = 10;` ` ` ` ` `if` `(bitsAreInAltOrder(n))` ` ` `document.write(` `"Yes"` `);` ` ` `else` ` ` `document.write(` `"No"` `);` ` ` ` ` `// This code is contributed by code_hunt.` `</script> ` |

**Output :**

Yes

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