Check whether the number has only first and last bits set
Given a positive integer n. The problem is to check whether only the first and last bits are set in the binary representation of n.
Examples:
Input : 9 Output : Yes (9)10 = (1001)2, only the first and last bits are set. Input : 15 Output : No (15)10 = (1111)2, except first and last there are other bits also which are set.
Approach: Following are the steps:
- If n == 1, return “Yes”.
- Else check whether n-1 is a power of 2. Refer this post.
C++
// C++ to check whether the number has only // first and last bits set #include <bits/stdc++.h> using namespace std; // function to check whether 'n' // is a power of 2 or not bool powerOfTwo(unsigned int n) { return (!(n & n-1)); } // function to check whether the number has only // first and last bits set bool onlyFirstAndLastAreSet(unsigned int n) { if (n == 1) return true; if (n == 2) return false; return powerOfTwo(n-1); } // Driver program to test above int main() { unsigned int n = 9; if (onlyFirstAndLastAreSet(n)) cout << "Yes"; else cout << "No"; return 0; } |
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Java
// Java program to check whether the // number has only first and last // bits set import java.util.*; class GFG { // function to check whether 'n' // is a power of 2 or not static boolean powerOfTwo(int n) { return ((n & n - 1) == 0); } // function to check whether the number has // only first and last bits set static boolean onlyFirstAndLastAreSet(int n) { if (n == 1) return true; return powerOfTwo(n-1); } // Driver program to test above public static void main (String[] args) { int n = Integer.parseUnsignedInt("9"); if (onlyFirstAndLastAreSet(n)) System.out.println("Yes"); else System.out.println("No"); } } /* This code is contributed by Mr. Somesh Awasthi */ |
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Python3
# Python3 program to check whether number # has only first and last bits set # function to check whether 'n' # is a power of 2 or not def powerOfTwo (n): return (not(n & n-1)) # function to check whether number # has only first and last bits set def onlyFirstAndLastAreSet (n): if (n == 1): return True return powerOfTwo (n-1) # Driver program to test above n = 9if (onlyFirstAndLastAreSet (n)): print('Yes') else: print('No') # This code is contributed by Shariq Raza |
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C#
// C# program to check whether the // number has only first and last // bits set using System; class GFG { // function to check whether 'n' // is a power of 2 or not static bool powerOfTwo(uint n) { return ((n & n - 1) == 0); } // function to check whether the number has // only first and last bits set static bool onlyFirstAndLastAreSet(uint n) { if (n == 1) return true; return powerOfTwo(n - 1); } // Driver program to test above public static void Main() { uint n = (uint)9; if (onlyFirstAndLastAreSet(n)) Console.WriteLine("Yes"); else Console.WriteLine("No"); } } // This code is contributed by Sam007 |
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PHP
<?php // PHP to check whether the number // has only first and last bits set // function to check whether 'n' // is a power of 2 or not function powerOfTwo($n) { return (!($n & $n - 1)); } // function to check whether // the number has only first // and last bits set function onlyFirstAndLastAreSet($n) { if ($n == 1) return true; if ($n == 2) return false; return powerOfTwo($n - 1); } // Driver Code $n = 9; if (onlyFirstAndLastAreSet($n)) echo "Yes"; else echo "No"; // This code is contributed // by Sach_Code ?> |
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Output:
Yes
This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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