add subsequence, substring

chapter11/subsequence.py

@@ -0,0 +1,54 @@
+import logging
+
+from tabulate import tabulate
+
+logging.basicConfig(
+    level=logging.DEBUG,
+    format="%(asctime)s %(levelname)s\n\r%(message)s",
+    datefmt="%H:%len_x:%S",
+)
+logger = logging.getLogger(__name__)
+
+
+def longest_common_subsequence(X, Y, len_x, len_y):
+    # create table and zero fill it
+    table = [[0 for _ in range(len_x + 1)] for _ in range(len_y + 1)]
+
+    for i in range(1, len_y + 1):
+        for j in range(1, len_x + 1):
+            if X[j - 1] == Y[i - 1]:
+                table[i][j] = table[i - 1][j - 1] + 1
+            else:
+                table[i][j] = max(table[i - 1][j], table[i][j - 1])
+
+    format_and_print(X, Y, table)
+
+    return table[-1][-1]
+
+
+def format_and_print(X, Y, table):
+    # enumerate first row (headings) + label each row in column0
+    for i, row in enumerate(table):
+        if i == 0:
+            continue
+        row[0] = Y[i - 1]
+    table[0] = [None, *X]
+
+    # print tabularised 2D array
+    logger.info(tabulate(table, tablefmt="pretty"))
+
+
+X = "fosh"
+Y = "fort"
+
+logger.info(f"words: {X} {Y}")
+longest_substring = longest_common_subsequence(X, Y, len(X), len(Y))
+print(f"Longest common subsequence: {longest_substring}")
+
+
+X = "fosh"
+Y = "fish"
+
+logger.info(f"words: {X} {Y}")
+longest_substring = longest_common_subsequence(X, Y, len(X), len(Y))
+print(f"Longest common subsequence: {longest_substring}")

chapter11/substring.py

@@ -0,0 +1,57 @@
+import logging
+
+from tabulate import tabulate
+
+logging.basicConfig(
+    level=logging.DEBUG,
+    format="%(asctime)s %(levelname)s\n\r%(message)s",
+    datefmt="%H:%M:%S",
+)
+logger = logging.getLogger(__name__)
+
+
+def longest_common_substring(X, Y, len_x, len_y):
+    # create table and zero fill it
+    table = [[0 for _ in range(len_x + 1)] for _ in range(len_y + 1)]
+
+    longest = 0
+
+    for i in range(1, len_y + 1):
+        for j in range(1, len_x + 1):
+            if X[j - 1] == Y[i - 1]:
+                table[i][j] = table[i - 1][j - 1] + 1
+                longest = max(longest, table[i][j])
+            else:
+                table[i][j] = 0
+
+    format_and_print(X, Y, table)
+
+    return longest
+
+
+def format_and_print(X, Y, table):
+    # enumerate first row (headings) + label each row in column0
+    for i, row in enumerate(table):
+        if i == 0:
+            continue
+        row[0] = Y[i - 1]
+    table[0] = [None, *X]
+
+    # print tabularised 2D array
+    logger.info(tabulate(table, tablefmt="pretty"))
+
+
+X = "fish"
+Y = "vish"
+
+logger.info(f"words: {X} {Y}")
+longest_substring = longest_common_substring(X, Y, len(X), len(Y))
+print(f"Longest common substring: {longest_substring}")
+
+
+X = "vista"
+Y = "hish"
+
+logger.info(f"words: {X} {Y}")
+longest_substring = longest_common_substring(X, Y, len(X), len(Y))
+print(f"Longest common substring: {longest_substring}")