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namespace ch_1;
public static class Ch1
{
public static void Main(string[] args)
{
var ints = args.Select(int.Parse).ToArray();
var middleIndex = ints.LeftRightSums()
.Select((sums, idx) => (sums, idx))
.FirstOrDefault(x => x.sums.leftSum == x.sums.rightSum,
defaultValue: (sums: (leftSum: 0, rightSum: 0), idx: -1))
.idx;
Console.WriteLine(middleIndex);
}
private static IEnumerable<(int leftSum, int rightSum)> LeftRightSums(this int[] ints)
{
var totalSum = ints.Sum();
var leftSum = 0;
foreach (var item in ints)
{
var rightSum = totalSum - leftSum - item;
yield return (leftSum, rightSum);
leftSum += item;
}
}
}
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