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Swap Two Numbers without using Temp Variable

GregEllis

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5.00/5 (4 votes)

18 Feb 2012CPOL 28.5K   1   5

You can do it with some XORs:int a = 25, b = 7;a = a ^ b;b = b ^ a;a = a ^ b;Or the same thing with some shorthand to make the code even harder to read:a ^= b;b ^= a;a ^= b;

You can do it with some XORs:

int a = 25, b = 7;

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

Or the same thing with some shorthand to make the code even harder to read:
a ^= b;
b ^= a;
a ^= b;

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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GregEllis

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Comments and Discussions

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swap without using temp variable iSkyTreasure29-Aug-12 6:09 iSkyTreasure 29-Aug-12 6:09  a=32 b=5 a=a+b //a=37 b=a-b //b=32 a=a-b //a=5 w/o vs with : which one is fastest? Alex Ten28-Apr-12 3:45 Alex Ten 28-Apr-12 3:45  performance wise, which is fastest? Probably the most useful varient of this was on the old IBM ... Chuck O'Toole19-Feb-12 9:17 Chuck O'Toole 19-Feb-12 9:17  Probably the most useful varient of this was on the old IBM 360 line which had "XC", Exclusive Or Characters, which could be used to swap up to 255 8 bit strings at a time. Single "int" temporaries are not as expensive then or now but whole blocks of memory for temps used to be expensive. Reason for my vote of 5 That's *the* established way since t... Andreas Gieriet19-Feb-12 8:18 Andreas Gieriet 19-Feb-12 8:18  Reason for my vote of 5 That's *the* established way since those old days when micro controllers had a few bytes of data memory and one could "not afford" to have a temp var in that very little memory. I prefer: a ^= b; b ^= a; a ^= b; because: 1. no overflow ... Huisheng Chen18-Feb-12 18:53 Huisheng Chen 18-Feb-12 18:53  I prefer: a ^= b; b ^= a; a ^= b; because: 1. no overflow like the one using addition 2. no external function required

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