Cantor pairing function

cantor_pairing.go

// http://en.wikipedia.org/wiki/Pairing_function
package main

import (
	"fmt"
	"math"
)

func InvertedCantorPairing(z int) (int, int) {
	w := int(math.Floor((math.Sqrt(float64(8*z+1)) - 1) / 2))
	t := (w*w + w) / 2
	y := z - t
	x := w - y
	return x, y
}

func CantorPairing(k1, k2 int) int {
	return (k1+k2)*(k1+k2+1)/2 + k2
}

func main() {
	for i := 0; i < 100; i++ {
		x, y := InvertedCantorPairing(i)
		fmt.Println(i, x, y, CantorPairing(x, y))
	}
}

Correct me if I'm wrong, but to avoid overflow with big (k1, k2) we should use
(k1/2+k2/2)*(k1+k2+1) + k2

This is similar in nature to what you'd do for

(a+b)/2

You'd instead code it as
a/2 + b/2

Because for large (a, b), where a+b > MAX_INT, we would still get a usable result.

@dyarosla -- rounding down for int division, we have:

(3+3)/2 = 6/2 = 3
3/2 + 3/2 = 1 + 1 = 2 

Your method works for approximate results, but not for exact ones.