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A pairing function (szudzik) that supports negative numbers
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| // src https://codepen.io/sachmata/post/elegant-pairing | |
| szudzik.getindex = function(x, y) { | |
| var xx = x >= 0 ? x * 2 : x * -2 - 1; | |
| var yy = y >= 0 ? y * 2 : y * -2 - 1; | |
| return (xx >= yy) ? (xx * xx + xx + yy) : (yy * yy + xx); | |
| }; | |
| szudzik.unpair = function(z) { | |
| var sqrtz = Math.floor(Math.sqrt(z)); | |
| var sqz = sqrtz * sqrtz; | |
| var result1 = ((z - sqz) >= sqrtz) ? [sqrtz, z - sqz - sqrtz] : [z - sqz, sqrtz]; | |
| var xx = result1[0] % 2 === 0 ? result1[0] / 2 : (result1[0] + 1) / -2; | |
| var yy = result1[1] % 2 === 0 ? result1[1] / 2 : (result1[1] + 1) / -2; | |
| return [xx, yy]; | |
| }; |
Author
Thank you for the fix, you're right!
Thanks nick and TheGreatRambler!
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Hi, i stumbled over your code while looking for a pairing function that works with negative numbers. After I reimplemented it in python I have noticed, that you have a small bug in the else branch of the following lines:
. In the else-branches of your
getindexfunction you multiply x respectively y with-2and then subtract1from the result. Therefore to invert this part of the function you need to first add1and then divide with-2.To correct this you have to change the mentioned lines to something like this:
Thanks,
Nick