Check if a number is positive, negative or zero using bit operators
Given a number N, check if it is positive, negative or zero without using conditional statements.
Examples:
Input : 30 Output : 30 is positive Input : -20 Output : -20 is negative Input: 0 Output: 0 is zero
The signed shift n>>31 converts every negative number into -1 and every other into 0.
When we do a -n>>31, if it is a positive number then it will return -1 as we are doing -n>>31 and the vice versa when we do for a negative number.
But when we do for 0 then n>>31 and -n>>31 both returns 0, so we get a formula:
1 + (n>>31) – (-n>>31)
..1) when n is negative :
1 +(-1)-0=0
..2) when n is positive:
1+0-(-1)=2
..3) when n is 0:
1+0-0=1
So we know it returns 0 when it is a negative number, it returns 1 when it is zero, returns 2 when it is a positive number.
So to not use if statements we store at 0th index “negative”, 1st index “zero” and at 2nd index “positive”, and print according to it.
CPP
// CPP program to find if a number is // positive, negative or zero using // bit wise operators. #include <iostream> using namespace std; // function to return 1 if it is zero // returns 0 if it is negative // returns 2 if it is positive int index( int i) { return 1 + (i >> 31) - (-i >> 31); } void check( int n) { // string array to store all kinds of number string s[] = { "negative" , "zero" , "positive" }; // function call to check the sign of number int val = index(n); cout << n << " is " << s[val] << endl; } // driver program to test the above function int main() { check(30); check(-20); check(0); return 0; } |
Java
// Java program to find if a number is // positive, negative or zero using // bit wise operators. class GFG { // function to return 1 if it is zero // returns 0 if it is negative // returns 2 if it is positive static int index( int i) { return 1 + (i >> 31 ) - (-i >> 31 ); } static void check( int n) { // string array to store all kinds // of number String s[] = { "negative" , "zero" , "positive" }; // function call to check the sign // of number int val = index(n); System.out.println(n + " is " + s[val]); } // Driver code public static void main(String[] args) { check( 30 ); check(- 20 ); check( 0 ); } } // This code is contributed by Anant Agarwal. |
Python3
# Python 3 program to # find if a number is # positive, negative # or zero using # bit wise operators. # function to return 1 if it is zero # returns 0 if it is negative # returns 2 if it is positive def index(i): return 1 + (i >> 31 ) - ( - i >> 31 ) def check(n): # string array to store all kinds of number s = "negative" , "zero" , "positive" # function call to check the sign of number val = index(n) print (n, "is" ,s[val]) # driver program to # test the above function check( 30 ) check( - 20 ) check( 0 ) # This code is contributed by # Smitha Dinesh Semwal |
C#
// C# program to find if a number is // positive, negative or zero using // bit wise operators. using System; class GFG { // function to return 1 if it is zero // returns 0 if it is negative // returns 2 if it is positive static int index( int i) { return 1 + (i >> 31) - (-i >> 31); } static void check( int n) { // string array to store all kinds of number String []s = { "negative" , "zero" , "positive" }; // function call to check the sign of number int val = index(n); Console.WriteLine(n + " is " + s[val]); } //Driver code public static void Main() { check(30); check(-20); check(0); } } // This code is contributed by Anant Agarwal. |
PHP
<?php // PHP program to find if a number is // positive, negative or zero using // bit wise operators. // function to return 1 if it is zero // returns 0 if it is negative // returns 2 if it is positive function index( $i ) { return 1 + ( $i >> 31) - (- $i >> 31); } function check( $n ) { // string array to store // all kinds of number $s = array ( "negative" , "zero" , "positive" ); // function call to check // the sign of number $val = index( $n ); echo $n , " is " , $s [ $val ], "\n" ; } // Driver Code check(30); check(-20); check(0); // This code is contributed by Ajit ?> |
Javascript
// JavaScript program to find if a number is positive, negative or zero // function to return 1 if it is zero, 0 if it is negative, and 2 if it is positive function index(i) { return 1 + (i >> 31) - (-i >> 31); } function check(n) { // string array to store all kinds of number let s = [ "negative" , "zero" , "positive" ]; // function call to check the sign of number let val = index(n); console.log(`${n} is ${s[val]}`); } // driver program to test the above function check(30); check(-20); check(0); |
Output:
30 is positive -20 is negative 0 is zero
Time Complexity : O(1)
Space Complexity : O(1)
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