Math.max method on array with equal values

Question

I'm working on some coderbyte code, and noticed that when I try to get the max item in an array of equal values undefined is returned. When logging the min value is logs 80 and not undefined. Why is this?

Updated Code:

function noRepeat(arr) {
    tmp = []
    if (arr.length === 2 && arr[0] === arr[1]) {
        return arr;
    }
    for (var i = 0;i<arr.length;i++) {
        if (tmp.indexOf(arr[i]) === -1) {
            tmp.push(arr[i])
        }
    }
    return tmp
}
function SecondGreatLow(arr) {
    arr = noRepeat(arr).sort(function (a,b) {return a-b;});
    var low = arr[arr.indexOf(Math.min.apply(Math,arr))+1];
    console.log("low",low);
    var high = arr[arr.indexOf(Math.max.apply(Math,arr))-1];
    console.log("high",high);
    return low +" "+high;
}
console.log(SecondGreatLow([80,80]));

Output:

"low" 80 
"high" undefined
"80 undefined"

Ahhh I literally figured this out right after posting... So the max method is working. It's returning the first instance of 80. When it tries to subtract 1 from index 0 the result is undefined because there is no value. :) — Rennix
– Rennix, Commented Jun 4, 2015 at 3:44
Exactly. Why are you trying to get the next \ previous item? — Yeldar Kurmangaliyev
– Yeldar Kurmangaliyev, Commented Jun 4, 2015 at 3:46
arr is sorted, why not use arr[0] and arr[arr.length - 1] to get low/high ? — lianbogo
– lianbogo, Commented Jun 4, 2015 at 3:48
Here is the problem set: Have the function SecondGreatLow(arr) take the array of numbers stored in arr and return the second lowest and second greatest numbers, respectively, separated by a space. For example: if arr contains [7, 7, 12, 98, 106] the output should be 12 98. The array will not be empty and will contain at least 2 numbers. It can get tricky if there's just two numbers! — Rennix
– Rennix, Commented Jun 4, 2015 at 3:49

Yeldar Kurmangaliyev · Accepted Answer · 2015-06-04 04:16:21Z

1

That's, actually, ok. How do you want to find the second largest \ smallest number in an array of two similar numbers? It should output "no solution" or something else. Just like there is no solution for an empty array.

function SecondGreatLow(arr) 
{
    arr = noRepeat(arr).sort(function (a,b) {return a-b;});
    if (arr.length < 2)
        return "No solution";
    console.log("low ", arr[1]);
    console.log("high ", arr[arr.length - 2]);
    return low + " " + high;
}

You don't need Math min and max functions as your array is sorted and values are unique. You need to take the second from beginning and the second from the end.

Also, you don't need this part as it is calculated right by algorithm.

if (arr.length === 2) 
{
    return arr[1] + " " + arr[0];
}

For example, you have an array [1, 1, 2].
You remove repetitions and get [1, 2].
Now your algorithms returns low = arr[1] = 2 and high = arr[2 - 2] = arr[0] = 1.
The answer is correct - 2 is the second minimum number and 1 is the second largest.

edited Jun 4, 2015 at 4:16

answered Jun 4, 2015 at 4:02

Yeldar Kurmangaliyev

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1 Comment

Rennix Over a year ago

Got it. That makes sense. I forgot to add that sometimes the array could be 2 values that are different. So if it were [12,39] I'd need the if statement "if (arr.length === 2 && arr[0] === arr[1])" for it to work as intended. Thanks for your help.

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