I'm running this (-3 >> 1) in java and getting answer -2 but according to me, it should be -1 as I'm thinking this like -3/2. Please help me understand this.
int x = -3 >> 1;
System.out.println(x + " " + (-3 >> 1));
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Abhinav Kinagi
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Aabid Husain
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@ItFreak That is wrong. Because `int` is signed and -3 is negative, you get a 1-bit when shifting to the right. – marstran Sep 05 '19 at 07:33
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oh yes youre right – ItFreak Sep 05 '19 at 07:34
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1Note also that **-1 >> 1 == -1** (Think of risking endless loops). `-n >> 1 == - (n/2) - (n%2)` – Joop Eggen Sep 05 '19 at 07:54
2 Answers
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The answer results from the binary representation of -3 in Java, which is
11111111111111111111111111111101
When you shift these bits right by one you get
11111111111111111111111111111110
Which is -2.
Eran
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As negetive numbers are saved as 2's complement value for arithmetic operations
Represent -3 in 2's complement
+3 -> 0011
complement ->1100
add 1 -> 0001
-3 -> 1101
after Right shift Operation the value will be 1110 as Right shift operation for negetive number add 1 to left-most bit.
link Why does right shifting negative numbers in C bring 1 on the left-most bits?
Represent -2 in 2's complement
+2 -> 0010
complement -> 1101
add 1 ->0001
-2 = -> 1110
AkashToSky
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