Update toeplitz-matrix.py

Python/toeplitz-matrix.py

@@ -1,6 +1,34 @@
 # Time:  O(m * n)
 # Space: O(1)
 
+# A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element.
+# Now given an M x N matrix, return True if and only if the matrix is Toeplitz.
+#
+# Example 1:
+#
+# Input: matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
+# Output: True
+# Explanation:
+# 1234
+# 5123
+# 9512
+#
+# In the above grid, the diagonals are
+# "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]",
+# and in each diagonal all elements are the same, so the answer is True.
+#
+# Example 2:
+#
+# Input: matrix = [[1,2],[2,2]]
+# Output: False
+# Explanation:
+# The diagonal "[1, 2]" has different elements.
+#
+# Note:
+# - matrix will be a 2D array of integers.
+# - matrix will have a number of rows and columns in range [1, 20].
+# - matrix[i][j] will be integers in range [0, 99].
+
 class Solution(object):
     def isToeplitzMatrix(self, matrix):
         """