Time: 1207 ms (14.22%), Space: 311.5 MB (5.37%) - LeetHub

Author: hogan-tech

1250-longest-common-subsequence/1250-longest-common-subsequence.py

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+# time complexity: O(n*m)
+# space compleixty: O(n*m)
+
+# Bottom Up
+from functools import lru_cache
+
+
+class Solution:
+    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
+        T1 = len(text1)
+        T2 = len(text2)
+        dp = [[0 for _ in range(T2 + 1)] for _ in range(T1 + 1)]
+        for t1 in range(1, T1 + 1):
+            for t2 in range(1, T2 + 1):
+                if text1[t1 - 1] == text2[t2 - 1]:
+                    dp[t1][t2] = dp[t1 - 1][t2 - 1] + 1
+                else:
+                    dp[t1][t2] = max(dp[t1 - 1][t2], dp[t1][t2 - 1])
+
+        return dp[T1][T2]
+
+
+# time complexity: O(n*m)
+# space compleixty: O(n*m)
+
+# Top Down
+class Solution:
+    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
+        T1 = len(text1)
+        T2 = len(text2)
+        dp = [[0 for _ in range(T2 + 1)] for _ in range(T1 + 1)]
+        for t1 in range(T1):
+            for t2 in range(T2):
+                if text1[t1] == text2[t2]:
+                    if t1 == 0 and t2 == 0:
+                        dp[t1][t2] = 1
+                    else:
+                        dp[t1][t2] = dp[t1-1][t2-1] + 1
+                if t1 > 0 and dp[t1-1][t2] > dp[t1][t2]:
+                    dp[t1][t2] = dp[t1-1][t2]
+                if t2 > 0 and dp[t1][t2-1] > dp[t1][t2]:
+                    dp[t1][t2] = dp[t1][t2-1]
+        return dp[T1 - 1][T2 - 1]
+
+
+class Solution:
+    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
+        @lru_cache(None)
+        def dp(p1: int, p2: int):
+            if p1 == len(text1) or p2 == len(text2):
+                return 0
+            if text1[p1] == text2[p2]:
+                return 1 + dp(p1 + 1, p2 + 1)
+            else:
+                return max(dp(p1, p2 + 1), dp(p1 + 1, p2))
+        return dp(0, 0)
+
+
+text1 = "abcde"
+text2 = "ace"
+print(Solution().longestCommonSubsequence(text1, text2))
+text1 = "abc"
+text2 = "abc"
+print(Solution().longestCommonSubsequence(text1, text2))
+text1 = "abc"
+text2 = "def"
+print(Solution().longestCommonSubsequence(text1, text2))