1 files changed, 65 insertions, 0 deletions
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
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+++ 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()