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

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?

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 ?