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EMC Interview Question for Developer Program Engineers


Country: United States



Comment hidden because of low score. Click to expand.
2
of 2 vote

a = a^b;
b = a^b;
a = a^b;

- Mir February 03, 2012 | Flag Reply
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0
of 0 votes

This works perfectly fine but fails when a is equal to b.
Should use an if condition before using this logic to check for a = b.

- Shekar Gurram February 03, 2012 | Flag
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0
of 0 votes

@mail.qurram : dude this works even if a=b;
suppose a=b=4 (100) . i.e. a=a^b makes a=000 ,b=a^b makes b=100 then a=a^b i.e (000)^(100) makes a=100...

- andykumar116 February 03, 2012 | Flag
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0
of 0 votes

I read about this long back. Just remember very little, but found out the actual thing which I intended to focus on. Although a very very specific case, its worth knowing it.

where you have written your code like this

swap(int *a, int *b)
{
  *a ^= *b ^= *a ^= *b;
}

Now, if suppose, by mistake, your code passes the two pointers to the same variable to this function. Guess what happens? Since Xor'ing an element with itself sets the variable to zero, this routine will end up setting the variable to zero (ideally it should have swapped the variable with itself). This scenario is quite possible in sorting algorithms which sometimes try to swap a variable with itself (maybe due to some small, but not so fatal coding error). One solution to this problem is to check if the numbers to be swapped are already equal to each other.

- Shekar Gurram February 03, 2012 | Flag
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1
of 1 vote

a = 5;
b = 6;
a = a + b;
b = a - b;
a = a - b;

- Anonymous February 03, 2012 | Flag Reply
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0
of 0 votes

This can fail in a case where the sum of a and b is greater than the integer max value.

- Shekar Gurram February 03, 2012 | Flag
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0
of 0 vote

This question is very well explained in (nobrainer.co.cc)

- Anony February 03, 2012 | Flag Reply
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0
of 0 votes

a=a+b-(b=a);

- Abhi February 03, 2012 | Flag
Comment hidden because of low score. Click to expand.
0
of 0 votes

a=a+b-(b=a);

- Abhi February 03, 2012 | Flag
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0
of 0 vote

a=10;
b=5;
a=a+b;
b=a-b;
a=a-b;

- D February 03, 2012 | Flag Reply
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0
of 0 vote

a=a+b-(b=a);

- Abhi February 03, 2012 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

a=a+b-(b=a);

- Abhi February 03, 2012 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

#define swap(x,y) x^=y^=x^=y

- Anonymous February 03, 2012 | Flag Reply
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0
of 0 vote

a=a^b^(a=b);

- kothabhaskar February 03, 2012 | Flag Reply
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0
of 0 vote

Should note it only works for integral types.

- Biff February 03, 2012 | Flag Reply
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0
of 0 vote

a=a & b; // a = a XOR b
b=b & a; // = b XOR (a XOR b) = a
a=a & b; // = (a XOR b) XOR a = b

- dave February 03, 2012 | Flag Reply
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0
of 0 votes

Oops, I mean ^

- dave February 03, 2012 | Flag
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0
of 0 vote

a=a+b;
b=a-b;
a=a-b;

- Anonymous July 01, 2015 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

a = a+b;
b = a-b;
a = a-b;

- Chitra July 01, 2015 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

a = a+b;
b = a-b;
a = a-b;

- Chitra July 01, 2015 | Flag Reply


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