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Author: Chris Wu

problems/longest-common-subsequence.py

@@ -0,0 +1,20 @@
+class Solution(object):
+    def longestCommonSubsequence(self, text1, text2):
+        M, N = len(text1), len(text2)
+        
+        #dp[i][j] := logest subsequence of text1[0:i-1] and text[0:j-1]
+        dp = [[0 for _ in xrange(N+1)] for _ in xrange(M+1)]
+            
+        for i in xrange(1, M+1):
+            for j in xrange(1, N+1):
+                if text1[i-1]==text2[j-1]:
+                    dp[i][j] = dp[i-1][j-1]+1
+                else:
+                    dp[i][j] = max(dp[i-1][j], dp[i][j-1])
+                    
+        return dp[M][N]
+
+"""
+Time: O(MN)
+Space: O(MN)
+"""

problems/maximum-length-of-repeated-subarray.py

@@ -0,0 +1,13 @@
+class Solution(object):
+    def findLength(self, A, B):
+        M, N = len(A), len(B)
+        
+        #dp[i][j] := the logest length of sub array that needs to involve A[i] and B[j]
+        dp = [[0 for _ in xrange(N+1)] for _ in xrange(M+1)]
+            
+        for i in xrange(1, M+1):
+            for j in xrange(1, N+1):
+                if A[i-1]==B[j-1]:
+                    dp[i][j] = dp[i-1][j-1]+1
+                    
+        return max(max(row) for row in dp)

problems/minimum-ascii-delete-sum-for-two-strings.py

@@ -0,0 +1,25 @@
+class Solution(object):
+    def minimumDeleteSum(self, s1, s2):
+        N, M = len(s1), len(s2)
+        dp = [[float('inf') for _ in xrange(M+1)] for _ in xrange(N+1)]
+        
+        dp[0][0] = 0
+        
+        for i in xrange(1, N+1):
+            dp[i][0] = dp[i-1][0]+ord(s1[i-1])
+            
+        for j in xrange(1, M+1):
+            dp[0][j] = dp[0][j-1]+ord(s2[j-1])
+        
+        for i in xrange(1, N+1):
+            for j in xrange(1, M+1):
+                if s1[i-1]==s2[j-1]:
+                    dp[i][j] = min(dp[i][j], dp[i-1][j-1])
+                dp[i][j] = min(dp[i][j], dp[i][j-1]+ord(s2[j-1]), dp[i-1][j]+ord(s1[i-1]))
+        
+        return dp[N][M]
+
+"""
+Time: O(MN)
+Space: O(MN)
+"""