3 files changed, 117 insertions, 0 deletions
diff --git a/challenge-257/sgreen/python/ch-1.py b/challenge-257/sgreen/python/ch-1.py
new file mode 100755
index 0000000000..f2ca928579
--- /dev/null
+++ b/challenge-257/sgreen/python/ch-1.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+import sys
+
+
+def smaller_than_current(ints: list) -> list:
+    """For each integer, how many integers are smaller than current one
+
+    Args:
+        ints (list): The input list of integers
+
+    Returns:
+        list: The output list of integers
+    """
+    return [sum(1 for j in ints if j < i) for i in ints]
+
+
+def main():
+    # Convert input into integers
+    array = [int(n) for n in sys.argv[1:]]
+    result = smaller_than_current(array)
+    print('(' + ', '.join(map(str, result)) + ')')
+
+
+if __name__ == '__main__':
+    main()
diff --git a/challenge-257/sgreen/python/ch-2.py b/challenge-257/sgreen/python/ch-2.py
new file mode 100755
index 0000000000..04eccc0243
--- /dev/null
+++ b/challenge-257/sgreen/python/ch-2.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+
+import json
+import sys
+
+
+def validate_matrix(matrix):
+    # Calculate the size of the matrix
+    rows = len(matrix)
+    cols = len(matrix[0])
+
+    for r in range(1, rows):
+        # Check that all columns are of equal length
+        if len(matrix[r]) != cols:
+            raise ValueError(f'Row {r} has different number of columns')
+
+
+def echelon(matrix: list) -> int:
+    # Check that the matrix is valid
+    validate_matrix(matrix)
+
+    # Get the position of the first one in each row
+    leading_one = [None if 1 not in row else row.index(1) for row in matrix]
+
+    for row_num in range(len(matrix)):
+        row = matrix[row_num]
+        leading_one_pos = leading_one[row_num]
+
+        # If the row is all zeros, there is nothing to check
+        if all(value == 0 for value in row):
+            continue
+
+        # Check the first non zero number is one
+        for value in row:
+            if value == 1:
+                break
+            if value != 0:
+                return 0
+
+        # Check if the leading one is further right
+        if row_num != 0:
+            if leading_one[row_num - 1] is None:
+                # The previous row was all zeros.
+                return 0
+            if leading_one[row_num - 1] > leading_one_pos:
+                # The previous first one was further to the right
+                return 0
+
+        # Count the number of non-zero values in the column that is the
+        #  leading one. It should be one (this row)
+        if sum(1 for row in matrix if row[leading_one_pos] != 0) != 1:
+            return 0
+
+    return 1
+
+
+def main():
+    # Convert input into a list of list of integers
+    matrix = json.loads(sys.argv[1])
+    result = echelon(matrix)
+    print(result)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/challenge-257/sgreen/python/test.py b/challenge-257/sgreen/python/test.py
new file mode 100755
index 0000000000..2e50bc4231
--- /dev/null
+++ b/challenge-257/sgreen/python/test.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+import unittest
+ch_1 = __import__('ch-1')
+ch_2 = __import__('ch-2')
+
+
+class TestClass(unittest.TestCase):
+    def test_ch_1(self):
+        self.assertEqual(ch_1.smaller_than_current([5, 2, 1, 6]), [2, 1, 0, 3])
+        self.assertEqual(ch_1.smaller_than_current([1, 2, 0, 3]), [1, 2, 0, 3])
+        self.assertEqual(ch_1.smaller_than_current([0, 1]), [0, 1])
+        self.assertEqual(ch_1.smaller_than_current([9, 4, 9, 2]), [2, 1, 2, 0])
+
+    def test_ch_2(self):
+        self.assertEqual(ch_2.echelon(
+            [[1, 0, 0, 1], [0, 1, 0, 2], [0, 0, 1, 3]]), 1)
+        self.assertEqual(ch_2.echelon([[1, 1, 0], [0, 1, 0], [0, 0, 0]]), 0)
+        self.assertEqual(ch_2.echelon(
+            [[0, 1, -2, 0, 1], [0, 0, 0, 1, 3], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]), 1)
+        self.assertEqual(ch_2.echelon(
+            [[1, 0, 0, 4], [0, 1, 0, 7], [0, 0, 1, -1]]), 1)
+
+
+if __name__ == '__main__':
+    unittest.main()