Create 1329_Sort_the_Matrix_Diagonally_(Medium).py

Turn matrix on 45 degrees, sort and then turn back

1329_Sort_the_Matrix_Diagonally_(Medium).py

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+class Solution:
+    def diagonalSort(self, mat: List[List[int]]) -> List[List[int]]:
+        if not mat: return [[]]
+        m = len(mat)
+        n = len(mat[0])
+        dlen = m + n - 1
+        diff = n - m     
+        diagonals = []
+        for i in range(dlen):
+            diagonals.append([])
+        for i in range(m):
+            for j in range(n):
+                diagonals[diff + i-j].append(mat[i][j])
+
+        for i in range(dlen):
+            diagonals[i] = sorted(diagonals[i])
+
+        for i in range(m):         
+            for j in range(n):
+                i_d = diff + i - j
+                j_d = min(j, i)
+                mat[i][j] = diagonals[i_d][j_d] 
+
+        return mat