smallest range

You have k lists of sorted integers in ascending order. Find the smallest range that includes at least one number from each of the k lists.

We define the range [a,b] is smaller than range [c,d] if b-a < d-c or a < c if b-a == d-c.

Example 1:

Input:[[4,10,15,24,26], [0,9,12,20], [5,18,22,30]]
Output: [20,24]
Explanation: 
List 1: [4, 10, 15, 24,26], 24 is in range [20,24].
List 2: [0, 9, 12, 20], 20 is in range [20,24].
List 3: [5, 18, 22, 30], 22 is in range [20,24].

Note:

The given list may contain duplicates, so ascending order means >= here.
1 <= k="" <="3500" -105="" of="" elements="" code="">

class Solution {
public:
    vector smallestRange(vector>& nums) {

    }
};

######思路：将所有数排序，并存储坐标，比对值与坐标找出最小的范围

class Solution {
public:
    vector smallestRange(vector>& nums) {
        vector res;
        vector> v;
        unordered_map m;
        for(int i=0;iv[right].first-v[left].first)
                {
                    diff=v[right].first-v[left].first;
                    res={v[left].first,v[right].first};
                }
                if(--m[v[left].second]==0) --cnt;
                ++left;
            }
        }
        return res;
    }
};