javascript - Finding a non-consecutive number pair in an array -

given array minimum length of 3 , maximum length of 5, contains uniquely occurring integers 0 4 in ascending order, need pick out 2 non-consecutive numbers it. non-consecutive refers numeric value, not position in array.

to clarify, here examples of valid arrays:

1. [ 1, 2, 3 ]
2. [ 0, 1, 2, 4 ]
3. [ 0, 3, 4 ]

for arrays above, valid answers be, respectively:

1. [ 1, 3 ]
2. [ 0, 2 ], [ 0, 4 ] or [ 1, 4 ]
3. [ 0, 3 ] or [ 0, 4 ]

furthermore, in cases there more 1 valid answer, need selected @ random, if @ possible (for instance don't want favor sequences begin lowest number, occur if began checking left right , stopped checking found 1 valid solution).

what efficient way of tackling problem in javascript?

you use 2 nested iterations , build new array choosing random result.

function getnonconsecutives(array) {      return array.reduce((r, a, i, aa) => r.concat(aa.slice(i + 2).map(b => [a, b])), []);  }    console.log(getnonconsecutives([ 0, 1, 2, 4 ]));

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according bee157's answer, use random choice constraint, length first index , add needed space second index.

the problem is, due nature of choosing first number first, distribution of result not equal.

function getnonconsecutives(array) {      var = math.floor(math.random() * (array.length - 2));      return [          array[i],          array[math.floor(math.random() * (array.length - 2 - i)) + 2 + i]      ];  }    console.log(getnonconsecutives([ 0, 1, 2, 4 ]));