Leetcode 1424. Diagonal Traverse II

Seawolf

Given a list of lists of integers, nums, return all elements of nums in diagonal order as shown in the below images.
 

Example 1:









Input: nums = [[1,2,3],[4,5,6],[7,8,9]]
Output: [1,4,2,7,5,3,8,6,9]
Example 2:









Input: nums = [[1,2,3,4,5],[6,7],[8],[9,10,11],[12,13,14,15,16]]
Output: [1,6,2,8,7,3,9,4,12,10,5,13,11,14,15,16]
Example 3:

Input: nums = [[1,2,3],[4],[5,6,7],[8],[9,10,11]]
Output: [1,4,2,5,3,8,6,9,7,10,11]
Example 4:

Input: nums = [[1,2,3,4,5,6]]
Output: [1,2,3,4,5,6]
 

Constraints:

1 <= nums.length <= 10^5
1 <= nums[i].length <= 10^5
1 <= nums[i][j] <= 10^9
There at most 10^5 elements in nums.

class Solution:
    def findDiagonalOrder(self, nums: List[List[int]]) -> List[int]:
        result = []
        if nums == None or len(nums) == 0:
            return result
        hashmap = collections.defaultdict(list)
        m = len(nums)
        for i in range(m):
            for j in range(len(nums[i])):
                hashmap[i + j].append(nums[i][j])
        for k in sorted(hashmap.keys()):
            temp = hashmap[k]
            temp = temp[::-1]
            result += temp
        return result