euler210.go

package main

import (
	"fmt"
	"math"
)

func main() {
	limit := int64(math.Pow(10, 8))
	ldiv4 := int64(limit / 4)
	ldiv8 := int64(limit / 8)
	ldiv8xrad2 := int64(float64(ldiv8) * math.Sqrt(2))
	sqrldiv8x2 := ldiv8 * ldiv8 * 2

	total := 3 * limit * limit / 2
	total = total + ldiv4*(ldiv4+1) - 2
	total = total + 4*(ldiv8xrad2-ldiv8)

	loopsum := int64(0)
	for x := ldiv8 + 1; x <= ldiv8xrad2; x++ {
		y := math.Sqrt(float64(sqrldiv8x2 - x*x))
		var ymax int64
		yfloor := math.Floor(y)
		if yfloor == y {
			ymax = int64(y - 1)
		} else {
			ymax = int64(yfloor)
		}
		loopsum += ymax
	}
	total = total + 8*loopsum

	fmt.Println(total)
}