Initial data commit

Task/Longest-common-subsequence/Python/longest-common-subsequence-3.py

@@ -0,0 +1,18 @@
+def lcs(a, b):
+    # generate matrix of length of longest common subsequence for substrings of both words
+    lengths = [[0] * (len(b)+1) for _ in range(len(a)+1)]
+    for i, x in enumerate(a):
+        for j, y in enumerate(b):
+            if x == y:
+                lengths[i+1][j+1] = lengths[i][j] + 1
+            else:
+                lengths[i+1][j+1] = max(lengths[i+1][j], lengths[i][j+1])
+
+    # read a substring from the matrix
+    result = ''
+    j = len(b)
+    for i in range(1, len(a)+1):
+        if lengths[i][j] != lengths[i-1][j]:
+            result += a[i-1]
+
+    return result