Create find-all-good-strings.py

Author: kamyu104

Python/find-all-good-strings.py

@@ -0,0 +1,53 @@
+# Time:  O(m * n)
+# Space: O(m)
+
+class Solution(object):
+    def findGoodStrings(self, n, s1, s2, evil):
+        """
+        :type n: int
+        :type s1: str
+        :type s2: str
+        :type evil: str
+        :rtype: int
+        """
+        MOD = 10**9+7
+        def getPrefix(pattern):
+            prefix = [-1]*len(pattern)
+            j = -1
+            for i in xrange(1, len(pattern)):
+                while j != -1 and pattern[j+1] != pattern[i]:
+                    j = prefix[j]
+                if pattern[j+1] == pattern[i]:
+                    j += 1
+                prefix[i] = j
+            return prefix
+    
+        prefix = getPrefix(evil)
+        dp = [[[[0]*len(evil) for _ in xrange(2)] for _ in xrange(2)] for _ in xrange(2)]
+        dp[0][0][0][0] = 1
+        for i in xrange(n):
+            dp[(i+1)%2] = [[[0]*len(evil) for _ in xrange(2)] for _ in xrange(2)]
+            for j in xrange(2):
+                for k in xrange(2):
+                    min_c = 'a' if j else s1[i]
+                    max_c = 'z' if k else s2[i]
+                    for l in xrange(len(evil)):
+                        if not dp[i%2][j][k][l]:
+                            continue
+                        for c in xrange(ord(min_c)-ord('a'), ord(max_c)-ord('a')+1):
+                            c = chr(c+ord('a'))
+                            m = l-1
+                            while m != -1 and evil[m+1] != c:
+                                m = prefix[m]
+                            if evil[m+1] == c:
+                                m += 1
+                            if m+1 == len(evil):
+                                continue
+                            dp[(i+1)%2][j or (s1[i] != c)][k or (s2[i] != c)][m+1] = \
+                                (dp[(i+1)%2][j or (s1[i] != c)][k or (s2[i] != c)][m+1] + dp[i%2][j][k][l]) % MOD
+        result = 0
+        for j in xrange(2):
+            for k in xrange(2):
+                for l in xrange(len(evil)):
+                    result = (result + dp[n%2][j][k][l]) % MOD
+        return result