498. Diagonal Traverse

https://leetcode.com/problems/diagonal-traverse

Python

Re-assemble

• Time: O(n*m)
• Space: O(n*m)

from collections import defaultdict


class Solution:
    def findDiagonalOrder(self, mat: List[List[int]]) -> List[int]:
        mapper = defaultdict(list)

        for i in range(len(mat)):
            for j in range(len(mat[i])):
                mapper[i+j].append(mat[i][j])

        result = []
        for key in sorted(mapper.keys()):
            if key % 2 == 0:
                result += mapper[key][::-1]
                continue
            result += mapper[key]

        return result