What does “”“ if((counter & (1 < 0): ”“” do?
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I am trying to print all subsets of an array. I came across this if statement in on of the solutions.
What does this if condition do?
if((counter & (1 << j)) > 0):
python python-3.x if-statement data-structures set
asked Nov 25 '18 at 5:35
I am LI am L
1219
add a comment |
I am trying to print all subsets of an array. I came across this if statement in on of the solutions.
What does this if condition do?
if((counter & (1 << j)) > 0):
python python-3.x if-statement data-structures set
asked Nov 25 '18 at 5:35
I am LI am L
1219
How do we know without knowing what iscounter,iandj?<<is bitwise left shift operator doc.
– Austin
Nov 25 '18 at 5:43
It checks if bit numberjincounteris set.
– Michael Butscher
Nov 25 '18 at 5:49
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33
add a comment |
I am trying to print all subsets of an array. I came across this if statement in on of the solutions.
What does this if condition do?
if((counter & (1 << j)) > 0):
python python-3.x if-statement data-structures set
asked Nov 25 '18 at 5:35
I am LI am L
1219
I am trying to print all subsets of an array. I came across this if statement in on of the solutions.
What does this if condition do?
if((counter & (1 << j)) > 0):
python python-3.x if-statement data-structures set
python python-3.x if-statement data-structures set
asked Nov 25 '18 at 5:35
I am LI am L
1219
asked Nov 25 '18 at 5:35
I am LI am L
1219
asked Nov 25 '18 at 5:35
I am LI am L
1219
asked Nov 25 '18 at 5:35
I am LI am L
1219
asked Nov 25 '18 at 5:35
I am LI am L
1219
1219
How do we know without knowing what iscounter,iandj?<<is bitwise left shift operator doc.
– Austin
Nov 25 '18 at 5:43
It checks if bit numberjincounteris set.
– Michael Butscher
Nov 25 '18 at 5:49
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33
add a comment |
How do we know without knowing what iscounter,iandj?<<is bitwise left shift operator doc.
– Austin
Nov 25 '18 at 5:43
It checks if bit numberjincounteris set.
– Michael Butscher
Nov 25 '18 at 5:49
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33
How do we know without knowing what is
counter, i and j ? << is bitwise left shift operator doc.– Austin
Nov 25 '18 at 5:43
How do we know without knowing what is
counter, i and j ? << is bitwise left shift operator doc.– Austin
Nov 25 '18 at 5:43
It checks if bit number
j in counter is set.– Michael Butscher
Nov 25 '18 at 5:49
It checks if bit number
j in counter is set.– Michael Butscher
Nov 25 '18 at 5:49
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33
add a comment |
2 Answers
2
active
oldest
votes
Your statement:
if ( (counter & (1 << j)) > 0 ):
It's some bitwise operations. Let's break it down:
(1 << j)generates the number0b1and shifts it left byjplaces -jmust be an integer. This is akin to saying2**j, or 2 to thejth power, but doing it with the bit-shifting operator<<makes it clear we're doing bitwise operations.
counter & (1 << j)takes the result of that last operation, and does a bitwiseandwith the variablecounter. It seems thatjis a specifier for a bitmask - it tells which bit is important to check in incounter. Since whatever(1 << j)produces will only have one1in its binary representation, the expressioncounter & (1 << j)will always produce either a power of 2, or 0.
> 0checks if the number that was produced was 0.
All in all, this is a fairly involved way to check if the jth bit from the right in counter is equal to 1 or 0. Without seeing the rest of your code, it's impossible to tell what the line does in context, but hopefully this gives you enough of a hint to whatever you're trying to figure out.
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
add a comment |
The & operator is a bitwise operator. More information here.
Basically, if we consider counter as a binary:
counter = 0b0010
1 << j -> with j = 0
j will be the position that you want to evaluate with the 1.
Therefore, in this case the IF statement will not be executed because the AND operator will return 0.
But with:
counter = 0b0010
1 << j -> with j = 1
The IF statement will be executed because the AND operator will return 1.
To understand a little more, you can play with the following piece of code and change the values of counter and j:
counter = 0b0100
j = 2
if((counter & (1 << j)) > 0):
print("True")
else:
print("False")
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Your statement:
if ( (counter & (1 << j)) > 0 ):
It's some bitwise operations. Let's break it down:
(1 << j)generates the number0b1and shifts it left byjplaces -jmust be an integer. This is akin to saying2**j, or 2 to thejth power, but doing it with the bit-shifting operator<<makes it clear we're doing bitwise operations.
counter & (1 << j)takes the result of that last operation, and does a bitwiseandwith the variablecounter. It seems thatjis a specifier for a bitmask - it tells which bit is important to check in incounter. Since whatever(1 << j)produces will only have one1in its binary representation, the expressioncounter & (1 << j)will always produce either a power of 2, or 0.
> 0checks if the number that was produced was 0.
All in all, this is a fairly involved way to check if the jth bit from the right in counter is equal to 1 or 0. Without seeing the rest of your code, it's impossible to tell what the line does in context, but hopefully this gives you enough of a hint to whatever you're trying to figure out.
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
add a comment |
Your statement:
if ( (counter & (1 << j)) > 0 ):
It's some bitwise operations. Let's break it down:
(1 << j)generates the number0b1and shifts it left byjplaces -jmust be an integer. This is akin to saying2**j, or 2 to thejth power, but doing it with the bit-shifting operator<<makes it clear we're doing bitwise operations.
counter & (1 << j)takes the result of that last operation, and does a bitwiseandwith the variablecounter. It seems thatjis a specifier for a bitmask - it tells which bit is important to check in incounter. Since whatever(1 << j)produces will only have one1in its binary representation, the expressioncounter & (1 << j)will always produce either a power of 2, or 0.
> 0checks if the number that was produced was 0.
All in all, this is a fairly involved way to check if the jth bit from the right in counter is equal to 1 or 0. Without seeing the rest of your code, it's impossible to tell what the line does in context, but hopefully this gives you enough of a hint to whatever you're trying to figure out.
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
add a comment |
Your statement:
if ( (counter & (1 << j)) > 0 ):
It's some bitwise operations. Let's break it down:
(1 << j)generates the number0b1and shifts it left byjplaces -jmust be an integer. This is akin to saying2**j, or 2 to thejth power, but doing it with the bit-shifting operator<<makes it clear we're doing bitwise operations.
counter & (1 << j)takes the result of that last operation, and does a bitwiseandwith the variablecounter. It seems thatjis a specifier for a bitmask - it tells which bit is important to check in incounter. Since whatever(1 << j)produces will only have one1in its binary representation, the expressioncounter & (1 << j)will always produce either a power of 2, or 0.
> 0checks if the number that was produced was 0.
All in all, this is a fairly involved way to check if the jth bit from the right in counter is equal to 1 or 0. Without seeing the rest of your code, it's impossible to tell what the line does in context, but hopefully this gives you enough of a hint to whatever you're trying to figure out.
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
Your statement:
if ( (counter & (1 << j)) > 0 ):
It's some bitwise operations. Let's break it down:
(1 << j)generates the number0b1and shifts it left byjplaces -jmust be an integer. This is akin to saying2**j, or 2 to thejth power, but doing it with the bit-shifting operator<<makes it clear we're doing bitwise operations.
counter & (1 << j)takes the result of that last operation, and does a bitwiseandwith the variablecounter. It seems thatjis a specifier for a bitmask - it tells which bit is important to check in incounter. Since whatever(1 << j)produces will only have one1in its binary representation, the expressioncounter & (1 << j)will always produce either a power of 2, or 0.
> 0checks if the number that was produced was 0.
All in all, this is a fairly involved way to check if the jth bit from the right in counter is equal to 1 or 0. Without seeing the rest of your code, it's impossible to tell what the line does in context, but hopefully this gives you enough of a hint to whatever you're trying to figure out.
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
answered Nov 25 '18 at 5:52
Green Cloak GuyGreen Cloak Guy
3,4201721
3,4201721
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
add a comment |
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:31
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:32
add a comment |
The & operator is a bitwise operator. More information here.
Basically, if we consider counter as a binary:
counter = 0b0010
1 << j -> with j = 0
j will be the position that you want to evaluate with the 1.
Therefore, in this case the IF statement will not be executed because the AND operator will return 0.
But with:
counter = 0b0010
1 << j -> with j = 1
The IF statement will be executed because the AND operator will return 1.
To understand a little more, you can play with the following piece of code and change the values of counter and j:
counter = 0b0100
j = 2
if((counter & (1 << j)) > 0):
print("True")
else:
print("False")
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
add a comment |
The & operator is a bitwise operator. More information here.
Basically, if we consider counter as a binary:
counter = 0b0010
1 << j -> with j = 0
j will be the position that you want to evaluate with the 1.
Therefore, in this case the IF statement will not be executed because the AND operator will return 0.
But with:
counter = 0b0010
1 << j -> with j = 1
The IF statement will be executed because the AND operator will return 1.
To understand a little more, you can play with the following piece of code and change the values of counter and j:
counter = 0b0100
j = 2
if((counter & (1 << j)) > 0):
print("True")
else:
print("False")
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
add a comment |
The & operator is a bitwise operator. More information here.
Basically, if we consider counter as a binary:
counter = 0b0010
1 << j -> with j = 0
j will be the position that you want to evaluate with the 1.
Therefore, in this case the IF statement will not be executed because the AND operator will return 0.
But with:
counter = 0b0010
1 << j -> with j = 1
The IF statement will be executed because the AND operator will return 1.
To understand a little more, you can play with the following piece of code and change the values of counter and j:
counter = 0b0100
j = 2
if((counter & (1 << j)) > 0):
print("True")
else:
print("False")
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
The & operator is a bitwise operator. More information here.
Basically, if we consider counter as a binary:
counter = 0b0010
1 << j -> with j = 0
j will be the position that you want to evaluate with the 1.
Therefore, in this case the IF statement will not be executed because the AND operator will return 0.
But with:
counter = 0b0010
1 << j -> with j = 1
The IF statement will be executed because the AND operator will return 1.
To understand a little more, you can play with the following piece of code and change the values of counter and j:
counter = 0b0100
j = 2
if((counter & (1 << j)) > 0):
print("True")
else:
print("False")
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
answered Nov 25 '18 at 6:05
Manuel ReyesManuel Reyes
886
886
add a comment |
add a comment |
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How do we know without knowing what is
counter,iandj?<<is bitwise left shift operator doc.– Austin
Nov 25 '18 at 5:43
It checks if bit number
jincounteris set.– Michael Butscher
Nov 25 '18 at 5:49
This was the program I was referrring to:geeksforgeeks.org/power-set
– I am L
Nov 25 '18 at 6:33