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2639 - Find the Width of Columns of a Grid (Easy)

https://leetcode.com/problems/find-the-width-of-columns-of-a-grid/

Problem Statement​

You are given a 0-indexed m x n integer matrix grid. The width of a column is the maximum lengthof its integers.

  • For example, if grid = [[-10], [3], [12]], the width of the only column is 3 since -10 is of length 3.

Return an integer array ans of size n where ans[i] is the width of the ith column.

The length of an integer x with len digits is equal to len if x is non-negative, and len + 1 otherwise.

Example 1:

Input: grid = [[1],[22],[333]]
Output: [3]
Explanation: In the 0th column, 333 is of length 3.

Example 2:

Input: grid = [[-15,1,3],[15,7,12],[5,6,-2]]
Output: [3,1,2]
Explanation: 
In the 0th column, only -15 is of length 3.
In the 1st column, all integers are of length 1. 
In the 2nd column, both 12 and -2 are of length 2.

Constraints:

  • m == grid.length
  • n == grid[i].length
  • 1 <= m, n <= 100
  • -109 <= grid[r][c] <= 109

Approach 1: Transpose and Count Digits​

The idea is to first transpose grid using zip. Then we calculate the number of digits and take the max. Alternatively we can convert to string and check the length.

Written by @wingkwong
class Solution:
    def findColumnWidth(self, grid: List[List[int]]) -> List[int]:
        def cal(x):
            res = 0
            if x == 0:
                res += 1
            if x < 0:
                res += 1
                x = -x
            while x > 0:
                x //= 10
                res += 1
            return res
        # we can further simplifed to
        # return [max(cal(y) for y in x) for x in zip(*grid)]
        res = []
        for x in zip(*grid):
            mx = 1
            for y in x:
                mx = max(mx, cal(y))
            res.append(mx)
        return res