## DEV Community

Abhishek Chaudhary

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# Sort the Matrix Diagonally

A matrix diagonal is a diagonal line of cells starting from some cell in either the topmost row or leftmost column and going in the bottom-right direction until reaching the matrix's end. For example, the matrix diagonal starting from `mat[2][0]`, where `mat` is a `6 x 3` matrix, includes cells `mat[2][0]`, `mat[3][1]`, and `mat[4][2]`.

Given an `m x n` matrix `mat` of integers, sort each matrix diagonal in ascending order and return the resulting matrix.

Example 1:

Input: mat = [[3,3,1,1],[2,2,1,2],[1,1,1,2]]
Output: [[1,1,1,1],[1,2,2,2],[1,2,3,3]]

Example 2:

Input: mat = [[11,25,66,1,69,7],[23,55,17,45,15,52],[75,31,36,44,58,8],[22,27,33,25,68,4],[84,28,14,11,5,50]]
Output: [[5,17,4,1,52,7],[11,11,25,45,8,69],[14,23,25,44,58,15],[22,27,31,36,50,66],[84,28,75,33,55,68]]

Constraints:

• `m == mat.length`
• `n == mat[i].length`
• `1 <= m, n <= 100`
• `1 <= mat[i][j] <= 100`

SOLUTION:

``````import bisect

class Solution:
def diagonalSort(self, mat: List[List[int]]) -> List[List[int]]:
m = len(mat)
n = len(mat[0])
diags = {}
for i in range(m):
for j in range(n):
if i - j in diags:
bisect.insort(diags[i - j], mat[i][j])
else:
diags[i - j] = [mat[i][j]]
for i in range(m):
for j in range(n):
mat[i][j] = diags[i - j][min(i, j)]
return mat

# import bisect

# class Solution:
#     def diagonalSort(self, mat: List[List[int]]) -> List[List[int]]:
#         m = len(mat)
#         n = len(mat[0])
#         vals = [[] for i in range(m + n - 1)]
#         curr = 0
#         for i in range(m):
#             x, y = i, 0
#             while x < m and y < n:
#                 bisect.insort(vals[curr], mat[x][y])
#                 x += 1
#                 y += 1
#             curr += 1
#         for i in range(1, n):
#             x, y = 0, i
#             while x < m and y < n:
#                 bisect.insort(vals[curr], mat[x][y])
#                 x += 1
#                 y += 1
#             curr += 1
#         curr = 0
#         for i in range(m):
#             x, y = i, 0
#             while x < m and y < n:
#                 mat[x][y] = vals[curr][y]
#                 x += 1
#                 y += 1
#             curr += 1
#         for i in range(1, n):
#             x, y = 0, i
#             while x < m and y < n:
#                 mat[x][y] = vals[curr][x]
#                 x += 1
#                 y += 1
#             curr += 1
#         return mat
``````