Create isomorphic-strings.py

kamyu104 · kamyu104 · commit 93ab11c2e4dd · 2015-04-29T16:41:48.000+08:00
diff --git a/Python/isomorphic-strings.py b/Python/isomorphic-strings.py
@@ -0,0 +1,40 @@
+# Time:  O(n)
+# Space: O(1)
+#
+# Given two strings s and t, determine if they are isomorphic.
+#
+# Two strings are isomorphic if the characters in s can be replaced to get t.
+#
+# All occurrences of a character must be replaced with another character 
+# while preserving the order of characters. No two characters may map to 
+# the same character but a character may map to itself.
+#
+# For example,
+# Given "egg", "add", return true.
+#
+# Given "foo", "bar", return false.
+#
+# Given "paper", "title", return true.
+#
+# Note:
+# You may assume both s and t have the same length.
+#
+
+class Solution:
+    # @param {string} s
+    # @param {string} t
+    # @return {boolean}
+    def isIsomorphic(self, s, t):
+        if len(s) != len(t):
+            return False
+    
+        return self.halfIsom(s, t) and self.halfIsom(t, s)
+
+    def halfIsom(self, s, t):
+        res = {}
+        for i in xrange(len(s)):
+            if s[i] not in res:
+                res[s[i]] = t[i]
+            elif res[s[i]] != t[i]:
+                return False
+        return True
