719. Find K-th Smallest Pair Distance

Given an integer array, return the k-th smallest distance among all the pairs. The distance of a pair (A, B) is defined as the absolute difference between A and B.

Example 1:

Input:
nums = [1,3,1]
k = 1
**Output: 0**
Explanation:
Here are all the pairs:
(1,3) -> 2
(1,1) -> 0
(3,1) -> 2
Then the 1st smallest distance pair is (1,1), and its distance is 0.

Note:

1. 2 <= len(nums) <= 10000.
2. 0 <= nums[i] < 1000000.
3. 1 <= k <= len(nums) * (len(nums) - 1) / 2.

# @lc code=start
using LeetCode

function smallest_distance_pair(nums::Vector{Int}, k::Int)::Int
    sort!(nums)
    n = length(nums)
    function count_not_greater(diff)
        i, ans = 1, 0
        for j in 2: n
            while nums[j] - nums[i] > diff
                i += 1
            ans += j - i
            end
        end

        return ans
    end

    left, right = 0, nums[end] - nums[1]
    while left <= right
        mid = (left + right) >> 1
        if count_not_greater(mid) >= k
            right = mid - 1
        else
            left = mid + 1
        end
    end

    return left
end
# @lc code=end

smallest_distance_pair (generic function with 1 method)

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