# Maximum distance between two 1’s in Binary representation of N

Given a number N, the task is to find the maximum distance between two 1’s in the binary representation of given N. Print -1 if binary representation contains less than two 1’s.**Examples:**

Input:N = 131Output:7 131 in binary = 10000011. The maximum distance between two 1's = 7.Input:N = 8Output:-1 8 in binary = 01000. It contains less than two 1's.

**Approach:**

- First find the binary representation of N.
- For each bit calculated, check if its a ‘1’.
- Store the index of first ‘1’ found in first_1, and the last ‘1’ found in last_1
- Then check if the last_1 is less than or equal to first_1. It will be the case when N is a power of 2. Hence print -1 in this case.
- In any other case, find the difference between the last_1 and first_1. This will be the required distance.

Below is the implementation of the above approach:

## C++

`// C++ program to find the` `// Maximum distance between two 1's` `// in Binary representation of N` `#include <bits/stdc++.h>` `using` `namespace` `std;` `int` `longest_gap(` `int` `N)` `{` ` ` `int` `distance = 0, count = 0,` ` ` `first_1 = -1, last_1 = -1;` ` ` `// Compute the binary representation` ` ` `while` `(N) {` ` ` `count++;` ` ` `int` `r = N & 1;` ` ` `if` `(r == 1) {` ` ` `first_1 = first_1 == -1` ` ` `? count` ` ` `: first_1;` ` ` `last_1 = count;` ` ` `}` ` ` `N = N / 2;` ` ` `}` ` ` `// if N is a power of 2` ` ` `// then return -1` ` ` `if` `(last_1 <= first_1) {` ` ` `return` `-1;` ` ` `}` ` ` `// else find the distance` ` ` `// between the first position of 1` ` ` `// and last position of 1` ` ` `else` `{` ` ` `distance = (last_1 - first_1);` ` ` `return` `distance;` ` ` `}` `}` `// Driver code` `int` `main()` `{` ` ` `int` `N = 131;` ` ` `cout << longest_gap(N) << endl;` ` ` `N = 8;` ` ` `cout << longest_gap(N) << endl;` ` ` `N = 17;` ` ` `cout << longest_gap(N) << endl;` ` ` `N = 33;` ` ` `cout << longest_gap(N) << endl;` ` ` `return` `0;` `}` |

## Java

`// Java program to find the` `// Maximum distance between two 1's` `// in Binary representation of N` `class` `GFG` `{` ` ` `static` `int` `longest_gap(` `int` `N)` ` ` `{` ` ` `int` `distance = ` `0` `, count = ` `0` `,` ` ` `first_1 = -` `1` `, last_1 = -` `1` `;` ` ` ` ` `// Compute the binary representation` ` ` `while` `(N != ` `0` `)` ` ` `{` ` ` `count++;` ` ` ` ` `int` `r = N & ` `1` `;` ` ` ` ` `if` `(r == ` `1` `)` ` ` `{` ` ` `first_1 = first_1 == -` `1` `?` ` ` `count : first_1;` ` ` `last_1 = count;` ` ` `}` ` ` `N = N / ` `2` `;` ` ` `}` ` ` ` ` `// if N is a power of 2` ` ` `// then return -1` ` ` `if` `(last_1 <= first_1)` ` ` `{` ` ` `return` `-` `1` `;` ` ` `}` ` ` ` ` `// else find the distance` ` ` `// between the first position of 1` ` ` `// and last position of 1` ` ` `else` ` ` `{` ` ` `distance = (last_1 - first_1);` ` ` `return` `distance;` ` ` `}` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `main (String[] args)` ` ` `{` ` ` `int` `N = ` `131` `;` ` ` `System.out.println(longest_gap(N));` ` ` ` ` `N = ` `8` `;` ` ` `System.out.println(longest_gap(N));` ` ` ` ` `N = ` `17` `;` ` ` `System.out.println(longest_gap(N));` ` ` ` ` `N = ` `33` `;` ` ` `System.out.println(longest_gap(N));` ` ` `}` `}` `// This code is contributed by AnkitRai01` |

## Python3

`# Python3 program to find the` `# Maximum distance between two 1's` `# in Binary representation of N` `def` `longest_gap(N):` ` ` `distance ` `=` `0` ` ` `count ` `=` `0` ` ` `first_1 ` `=` `-` `1` ` ` `last_1 ` `=` `-` `1` ` ` `# Compute the binary representation` ` ` `while` `(N > ` `0` `):` ` ` `count ` `+` `=` `1` ` ` `r ` `=` `N & ` `1` ` ` `if` `(r ` `=` `=` `1` `):` ` ` `if` `first_1 ` `=` `=` `-` `1` `:` ` ` `first_1 ` `=` `count` ` ` `else` `:` ` ` `first_1 ` `=` `first_1` ` ` `last_1 ` `=` `count` ` ` `N ` `=` `N ` `/` `/` `2` ` ` `# if N is a power of 2` ` ` `# then return -1` ` ` `if` `(last_1 <` `=` `first_1):` ` ` `return` `-` `1` ` ` ` ` `# else find the distance` ` ` `# between the first position of 1` ` ` `# and last position of 1` ` ` `else` `:` ` ` `distance ` `=` `last_1 ` `-` `first_1` ` ` `return` `distance` `# Driver code` `N ` `=` `131` `print` `(longest_gap(N))` `N ` `=` `8` `print` `(longest_gap(N))` `N ` `=` `17` `print` `(longest_gap(N))` `N ` `=` `33` `print` `(longest_gap(N))` `# This code is contributed by Mohit Kumar` |

## C#

`// C# program to find the` `// Maximum distance between two 1's` `// in Binary representation of N` `using` `System;` `class` `GFG` `{` ` ` `static` `int` `longest_gap(` `int` `N)` ` ` `{` ` ` `int` `distance = 0, count = 0,` ` ` `first_1 = -1, last_1 = -1;` ` ` ` ` `// Compute the binary representation` ` ` `while` `(N != 0)` ` ` `{` ` ` `count++;` ` ` ` ` `int` `r = N & 1;` ` ` ` ` `if` `(r == 1)` ` ` `{` ` ` `first_1 = first_1 == -1 ?` ` ` `count : first_1;` ` ` `last_1 = count;` ` ` `}` ` ` `N = N / 2;` ` ` `}` ` ` ` ` `// if N is a power of 2` ` ` `// then return -1` ` ` `if` `(last_1 <= first_1)` ` ` `{` ` ` `return` `-1;` ` ` `}` ` ` ` ` `// else find the distance` ` ` `// between the first position of 1` ` ` `// and last position of 1` ` ` `else` ` ` `{` ` ` `distance = (last_1 - first_1);` ` ` `return` `distance;` ` ` `}` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `Main (String []args)` ` ` `{` ` ` `int` `N = 131;` ` ` `Console.WriteLine(longest_gap(N));` ` ` ` ` `N = 8;` ` ` `Console.WriteLine(longest_gap(N));` ` ` ` ` `N = 17;` ` ` `Console.WriteLine(longest_gap(N));` ` ` ` ` `N = 33;` ` ` `Console.WriteLine(longest_gap(N));` ` ` `}` `}` `// This code is contributed by Arnab Kundu` |

## Javascript

`<script>` `// Javascript program to find the` `// Maximum distance between two 1's` `// in Binary representation of N` `function` `longest_gap(N)` `{` ` ` `let distance = 0, count = 0,` ` ` `first_1 = -1, last_1 = -1;` ` ` `// Compute the binary representation` ` ` `while` `(N) {` ` ` `count++;` ` ` `let r = N & 1;` ` ` `if` `(r == 1) {` ` ` `first_1 = first_1 == -1` ` ` `? count` ` ` `: first_1;` ` ` `last_1 = count;` ` ` `}` ` ` `N = parseInt(N / 2);` ` ` `}` ` ` `// if N is a power of 2` ` ` `// then return -1` ` ` `if` `(last_1 <= first_1) {` ` ` `return` `-1;` ` ` `}` ` ` `// else find the distance` ` ` `// between the first position of 1` ` ` `// and last position of 1` ` ` `else` `{` ` ` `distance = (last_1 - first_1);` ` ` `return` `distance;` ` ` `}` `}` `// Driver code` ` ` `let N = 131;` ` ` `document.write(longest_gap(N) + ` `"<br>"` `);` ` ` `N = 8;` ` ` `document.write(longest_gap(N) + ` `"<br>"` `);` ` ` `N = 17;` ` ` `document.write(longest_gap(N) + ` `"<br>"` `);` ` ` `N = 33;` ` ` `document.write(longest_gap(N) + ` `"<br>"` `);` `</script>` |

**Output**

7 -1 4 5

**Time Complexity:**** **O(log N)

* Auxiliary Space:* O(1)