Smallest Range Covering Elements from K Lists

Statement

You are given $k$ sorted lists of integers, nums, where each list in nums is in non-decreasing order. Your task is to find the smallest range that contains at least one element from each of the $k$ lists.

A range $[a,b]$ is considered smaller than another range $[c,d]$ if $b−a<d−c$, or $a < c$ if $b-a==d-c$.

Constraints:

• nums.length $== k$

• $1 <= k <= 100$

• $1 \leq$ nums[i].length $\leq 50$

• $-10^3 \leq$ nums[i][j] $\leq10^3$

• nums[i] is sorted in a non-decreasing order.

Examples