Binary Search: https://www.khanacademy.org/computing/computer-science/algorithms/binary-search/a/binary-search
for start + 1 < end {
mid := (end-start)/2+start
if nums[mid] > target {
end = mid
} else {
start = mid
}
}
if nums[start] == target {
return start
} else if nums[end] == target {
return end
}
return -1 // not within array