103. implement Math.sqrt()

Math.sqrt() helps us getting the square root of a number.

Can your write your own mySqrt() ? You should return the integer part only, truncating the fraction part.

mySqrt(0)
// 1

mySqrt(1)
// 1

mySqrt(2)
// 1

mySqrt(4)
// 2

mySqrt(NaN)
// NaN

Attention for the special case listed up in the spec.

Follow-up

What is time & space complexity of your solution ? Can you do better?