I have to multiply the sign of all elements in an array.
For example 1:
input: [1, 2, 3]
output: 1
Explain: 1 * 1 * 1 = 1
Ex2:
input: [1, -2, 3]
output: -1
Explain: 1 * (-1) * 1 = -1
Ex3:
input: [1, -2, 3, 0]
output: 0
Explain: 1 * (-1) * 1 * 0 = 0
And here is my solution
function cal(A)
{
return A.reduce((total, currentValue) => total * Math.sign(currentValue), 1);
}
However, the output of ex3 cal([1, -2, 3, 0])
is -0
.
I've already thought about adding one more condition like this
function cal(A)
{
var total = A.reduce((total, currentValue) => total * Math.sign(currentValue), 1);
if(total === 0)
return 0;
else
return total;
}
And obviously, It looks ugly. Is there a more elegant way to resolve that?
In order to avoid conditional checks and keep the function purely computational you can use the curious rules of -0
to simply add 0 to the result of your reduce()
which will have no effect on non-zero results but will have the effect of converting -0
to 0
.
function cal(arr) {
return arr.reduce((a, c) => a * Math.sign(c), 1) + 0;
}
console.log(cal([1, 2, 3])); // 1
console.log(cal([1, -2, 3])); // -1
console.log(cal([1, -2, 3, 0])); // 0
See signed zero for more general discussion.