Create minimum-insertion-steps-to-make-a-string-palindrome.py

Author: kamyu104

Python/minimum-insertion-steps-to-make-a-string-palindrome.py

@@ -0,0 +1,20 @@
+# Time:  O(n^2)
+# Space: O(n)
+
+class Solution(object):
+    def minInsertions(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        def longestCommonSubsequence(text1, text2):
+            if len(text1) < len(text2):
+                return self.longestCommonSubsequence(text2, text1)
+            dp = [[0 for _ in xrange(len(text2)+1)] for _ in xrange(2)]
+            for i in xrange(1, len(text1)+1):
+                for j in xrange(1, len(text2)+1):
+                    dp[i%2][j] = dp[(i-1)%2][j-1]+1 if text1[i-1] == text2[j-1] \
+                                 else max(dp[(i-1)%2][j], dp[i%2][j-1])
+            return dp[len(text1)%2][len(text2)]
+
+        return len(s)-longestCommonSubsequence(s, s[::-1])