I’m reading a C# book for beginners, and in every end of the chapter, there are exercises to be answered based on the lessons tackled.
One of those exercises goes this way: (not the exact wordings)
Write a program that will accept an int as the array length, and the values for the array.
Then will print:
“0” if the array is not sorted in ascending way.
“1” if it is sorted. And,
“2” if it is sorted, but there are duplicates.
Example:
// Sorted
Input: 1, 2, 3, 5
Print: 1
// Not sorted
Input: 2, 1, 3, 6
Print: 0
// Sorted, but with duplicates
Input: 2, 2, 3, 7
Print: 2
I don’t know if my logic here is absolute, but somehow it is working,
and I done it in my way using this code:
int arrayLength = 0;
int prev, next;
int sortStatus = 1;
Console.Write("Input array Length: ");
arrayLength = Convert.ToInt32(Console.ReadLine());
int ar = new intarrayLength;
for (int x = 0; x < arrayLength; x++)
{
Console.Write("Input {0} value: ", (x+1).ToString());
arx = Convert.ToInt32(Console.ReadLine());
}
for (int x = 0; x < ar.Length-1; x++)
{
prev = (int)arx;
next = (int)arx + 1;
if (next < prev)
sortStatus = 0;
if (next == prev)
sortStatus = 2;
}
Console.Write(sortStatus.ToString());
Console.Read();
Is it possible to express this in LINQ? How?
,
if (ar.SequenceEqual(ar.OrderBy(x => x)))
{
if (ar.Distinct().Count() == ar.Length)
return 1;
else
return 2;
}
else
{
return 0;
}
,
A pure LINQ alternative … (for academic interest only (but probably still faster than the accepted answer!)
var input = new int { 1, 2, 3, 4, 5 };
var output = input.Zip(input.Skip(1), (a, b) => new {a=a, b=b})
.Aggregate(1, (status, x) => status == 0 ? 0 : ((x.a > x.b ? 0 : (x.a == x.b ? 2 : status))));
,
As a note, your expressed non-LINQ logic has a flaw.
if (next < prev)
sortStatus = 0;
if (next == prev)
sortStatus = 2;
Your rule says that the array must be sorted ascending but have duplicates in order to get an output of 2. However, your logic will return 2 for { 1, 9, 7, 7 }
.
Another way to write your code might be the following. (This is not using LINQ, but this is too long to post as a comment to your question.)
static int EvaluateArray(int array)
{
int? lastItem = null;
bool match = false;
foreach (int item in array)
{
if (item < lastItem)
return 0;
else if (item == lastItem)
match = true;
lastItem = item;
}
if (match)
return 2;
return 1;
}
In this method, we will early-return as soon as we have an item less than the previous item. Otherwise, we will set a boolean if we come across a matching value. At the end of the loop, we know the array is sorted ascending. The only thing left is check if there was a match.
,
Untested.
IEnumerable<int> signs =
from i in Enumerable.Range(0, ar.Length).Skip(1)
select ari-1.CompareTo(ari);
int result =
signs.Any(sign => sign < 0) ? 0 :
signs.All(sign => 0 < sign) ? 1 :
2;
Also untested:
int minSign = !ar.Skip(1).Any() ? 1 :
(
from i in Enumerable.Range(0, ar.Length).Skip(1)
select ari-1.CompareTo(ari)
).TakeWhile(x => 0 <= x).Min();
int result =
minSign < 0 ? 0 :
0 < minSign ? 1 :
2;