Thanks,
I thought that contact means having a common border not just a corner.

Sure! field[5][4] contacts with field[6][3]
It's funny I was stuck on that too today.

Theres a submarine which touches a cruiser, isn't there?

for this test-case :
{{1,0,0,0,0,1,1,0,0,0},
{1,0,1,0,0,0,0,0,1,0},
{1,0,1,0,1,1,1,0,1,0},
{1,0,0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0,1,0},
{0,0,0,0,1,1,1,0,0,0},
{0,0,0,1,0,0,0,0,1,0},
{0,0,0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,1,0,0},
{0,0,0,0,0,0,0,0,0,0}}
I am getting :
Must return false if ships are in contact expected: but was:
Can some one tell me how this input has contacted ships?

4-3 < 5-1

In which case, the instructions should say that.

Yes, if you imagine the answer to be [x, y] then the result given must be the one with the lowest value of y.

The 7 is before the second 5

Could someone please explain to me , How entire pair could be earlier ?
for example :
sum_pairs([10, 5, 2, 3, 7, 5], 10)

^-----------^ 5 + 5 = 10, indices: 1, 5

^--^ 3 + 7 = 10, indices: 3, 4 *

* entire pair is earlier, and therefore is the correct answer

== [3, 7]
Why [3,7] is the answer ?