find-smallest-common-element-in-all-rows

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1198. Find Smallest Common Element in All Rows (Medium)

Given a matrix mat where every row is sorted in increasing order, return the smallest common element in all rows.

If there is no common element, return -1.

 

Example 1:

Input: mat = [[1,2,3,4,5],[2,4,5,8,10],[3,5,7,9,11],[1,3,5,7,9]]
Output: 5

 

Constraints:

• 1 <= mat.length, mat[i].length <= 500
• 1 <= mat[i][j] <= 10^4
• mat[i] is sorted in increasing order.

Related Topics

[Hash Table] [Binary Search]

Hints

Hint 1

Notice that each row has no duplicates.

Hint 2

Is counting the frequency of elements enough to find the answer?

Hint 3

Use a data structure to count the frequency of elements.

Hint 4

Find an element whose frequency equals the number of rows.