indeed, the PHP, Haskell and C# version have undue (since this kata is about how to define mutually recursive functions, not how to optimize the sequence generation) performance tests

there is an open issue regarding this

For those interested in understanding: The 10 expected is the position in the array, not the integer value of a peak

Your solution is not correct (read the description, you are not doing what is requested). The C# translation is fine.

This is the best answer here. All you have to do is change one word...

This is due to the lack of random tests, already pointed out.

C#

Which language?

Loved this one.

Worst kata I've seen in my whole life.

Yes. Copying the input instead fixed it. Never had this problem before so I had no idea it was even a thing. I've noticed some Katas mention mutating inputs in their description, but never actually knew why. Thanks!

C#: Tests are susceptible to mutation of input and fail in confusing way when input list is modified (see the issue from qrt88 below).

I just checked the C# version of the kata and it seems to work OK for me.
Do you mutate the input list by any chance?

C# - Clearly something going on with random tests. Logged input and output and this is what I got:

Input:
4500, 733, 4976, 9018, 8542, 4520, 9616, 5532, 4302, 6802, 1606, 1265, 9465, 2552, 7297, 2718, 2495, 2752, 3031, 9920, 6172, 5303, 385, 1202, 9738, 2355, 8739, 6243, 1340, 8043, 8160, 9237, 5294, 4386, 9016, 7802, 9730, 3961, 932, 4706, 5700, 2688, 629, 8813, 7524, 1255, 8957, 7794, 6844, 1672, 1215, 7540, 8370, 5425, 2237, 9196, 353, 3780, 9280, 6192, 5781, 3378, 4198, 6258, 8641, 2369, 5971, 5084, 3536, 9495, 2988, 8533, 1826, 8325, 4226, 3490, 4680, 1572, 3677, 8488, 3398, 951, 9399, 9667, 6833, 625, 872, 9868, 2155, 9819, 7455, 5955, 4681, 4739, 8925, 2327, 8489, 4370, 177, 5161, 5284, 3878, 4263, 7349, 8683, 2682, 5720, 51, 1204, 8747, 4521, 8781, 108, 797, 2800, 4835, 3979, 4530, 9425, 8022, 1502, 6102, 2935, 3716, 2045, 7032, 3857, 7087, 1905, 5000, 316, 1400, 8516, 3210, 9520, 6687, 2055, 990, 4156, 4905, 826, 8670, 3408, 8673, 5853, 3890, 1944, 4096, 8347, 3964, 4945, 3664, 9181, 948, 552, 5309, 1656, 8824, 8632, 652, 9299, 3752, 4211, 7386, 1591, 7586, 3280, 8147, 1929, 3546, 5274, 3123, 681, 7432, 9526, 8412, 3372, 1185, 9967, 5148

Output:
9967, 51, 9920, 108, 9868, 177, 9819, 316, 9738, 353, 9730, 385, 9667, 552, 9616, 625, 9526, 629, 9520, 652, 9495, 681, 9465, 733, 9425, 797, 9399, 826, 9299, 872, 9280, 932, 9237, 948, 9196, 951, 9181, 990, 9018, 1185, 9016, 1202, 8957, 1204, 8925, 1215, 8824, 1255, 8813, 1265, 8781, 1340, 8747, 1400, 8739, 1502, 8683, 1572, 8673, 1591, 8670, 1606, 8641, 1656, 8632, 1672, 8542, 1826, 8533, 1905, 8516, 1929, 8489, 1944, 8488, 2045, 8412, 2055, 8370, 2155, 8347, 2237, 8325, 2327, 8160, 2355, 8147, 2369, 8043, 2495, 8022, 2552, 7802, 2682, 7794, 2688, 7586, 2718, 7540, 2752, 7524, 2800, 7455, 2935, 7432, 2988, 7386, 3031, 7349, 3123, 7297, 3210, 7087, 3280, 7032, 3372, 6844, 3378, 6833, 3398, 6802, 3408, 6687, 3490, 6258, 3536, 6243, 3546, 6192, 3664, 6172, 3677, 6102, 3716, 5971, 3752, 5955, 3780, 5853, 3857, 5781, 3878, 5720, 3890, 5700, 3961, 5532, 3964, 5425, 3979, 5309, 4096, 5303, 4156, 5294, 4198, 5284, 4211, 5274, 4226, 5161, 4263, 5148, 4302, 5084, 4370, 5000, 4386, 4976, 4500, 4945, 4520, 4905, 4521, 4835, 4530, 4739, 4680, 4706, 4681

Test Failed
Expected is <System.Collections.Generic.List1[System.Int32]> with 0 elements, actual is <System.Collections.Generic.List1[System.Int32]> with 180 elements
Values differ at index [0]
Extra: < 9967, 51, 9920... >

Here's from another run:

Input:
6868, 9021, 9720, 5672, 453, 9297, 4984, 8283, 7854, 1996, 4810, 3808, 1036, 2525, 754, 954, 9980, 9765, 1142, 7592, 2801, 9072, 1476, 1608, 566, 3553, 8919, 5430, 7829, 1537, 1930, 8905, 2368, 7596, 504, 3427, 2058, 867, 1216, 110, 9336, 2438, 6224, 4730, 3405, 3154, 1217, 5266, 9963, 3463, 4663, 4818, 9328, 4734, 7795, 7550, 8117, 5112, 6899, 383, 9553, 459, 6323, 72, 5904, 1446, 3439, 2027, 7327, 2671, 7927, 8904, 9926, 7487, 3465, 6639, 5252, 6878, 7160, 404, 7708, 170, 7866, 8073, 7266, 4093, 3039, 2867, 2708, 5877, 171, 6945, 3967, 838, 556, 8882, 6114, 6158, 8825, 1965, 9715, 9190, 7939, 7298, 5535, 5759, 4891, 1847, 1275, 1162, 2304, 1245, 7952, 6501, 2675, 9389, 2592, 8250, 2805, 1817, 8406, 577, 9318, 1456, 2505, 988, 4942, 9093, 6936, 4582, 530, 8052, 5200, 688, 8517, 2230, 574, 2543, 1513, 9201, 1198, 1598, 1552, 3578, 8926, 8992, 7465, 8162, 1167, 6295, 7864, 3359, 7013, 3559, 9143, 9871, 6489, 4798, 4553, 822, 5798, 4910, 6692, 637, 3210, 3192, 2757, 5818, 4158, 7165, 2023, 5712, 1298

Input Count: 173

Output:
9980, 72, 9963, 110, 9926, 170, 9871, 171, 9765, 383, 9720, 404, 9715, 453, 9553, 459, 9389, 504, 9336, 530, 9328, 556, 9318, 566, 9297, 574, 9201, 577, 9190, 637, 9143, 688, 9093, 754, 9072, 822, 9021, 838, 8992, 867, 8926, 954, 8919, 988, 8905, 1036, 8904, 1142, 8882, 1162, 8825, 1167, 8517, 1198, 8406, 1216, 8283, 1217, 8250, 1245, 8162, 1275, 8117, 1298, 8073, 1446, 8052, 1456, 7952, 1476, 7939, 1513, 7927, 1537, 7866, 1552, 7864, 1598, 7854, 1608, 7829, 1817, 7795, 1847, 7708, 1930, 7596, 1965, 7592, 1996, 7550, 2023, 7487, 2027, 7465, 2058, 7327, 2230, 7298, 2304, 7266, 2368, 7165, 2438, 7160, 2505, 7013, 2525, 6945, 2543, 6936, 2592, 6899, 2671, 6878, 2675, 6868, 2708, 6692, 2757, 6639, 2801, 6501, 2805, 6489, 2867, 6323, 3039, 6295, 3154, 6224, 3192, 6158, 3210, 6114, 3359, 5904, 3405, 5877, 3427, 5818, 3439, 5798, 3463, 5759, 3465, 5712, 3553, 5672, 3559, 5535, 3578, 5430, 3808, 5266, 3967, 5252, 4093, 5200, 4158, 5112, 4553, 4984, 4582, 4942, 4663, 4910, 4730, 4891, 4734, 4818, 4798, 4810

Output Count: 173

Test Failed
Expected is <System.Collections.Generic.List1[System.Int32]> with 1 elements, actual is <System.Collections.Generic.List1[System.Int32]> with 173 elements
Values differ at index [0]
Expected: 4810
But was: 9980

Sample tests look like this and is working fine:

Input: 15, 11, 10, 7, 12

Output: 15, 7, 12, 10, 11

Input: 91, 75, 86, 14, 82

Output: 91, 14, 86, 75, 82

Input: 84, 79, 76, 61, 78

Output: 84, 61, 79, 76, 78

Input: 52, 77, 72, 44, 74, 76, 40

Output: 77, 40, 76, 44, 74, 52, 72

Input: 1, 6, 9, 4, 3, 7, 8, 2

Output: 9, 1, 8, 2, 7, 3, 6, 4

Input: 78, 79, 52, 87, 16, 74, 31, 63, 80

Output: 87, 16, 80, 31, 79, 52, 78, 63, 74

So what's up?

If there's a translation for it in a language, it's possible in that language.

Is this even possible using C#?