Create decode-string.py

Author: kamyu104

Python/decode-string.py

@@ -0,0 +1,47 @@
+# Time:  O(n)
+# Space: O(h), h is the depth of the recursion
+
+# Given an encoded string, return it's decoded string.
+#
+# The encoding rule is: k[encoded_string], 
+# where the encoded_string inside the square brackets is 
+# being repeated exactly k times. Note that k is guaranteed
+# to be a positive integer.
+#
+# You may assume that the input string is always valid;
+# No extra white spaces, square brackets are well-formed, etc.
+#
+# Furthermore, you may assume that the original data does not
+# contain any digits and that digits are only for those repeat numbers, k.
+# For example, there won't be input like 3a or 2[4].
+#
+# Examples:
+#
+# s = "3[a]2[bc]", return "aaabcbc".
+# s = "3[a2[c]]", return "accaccacc".
+# s = "2[abc]3[cd]ef", return "abcabccdcdcdef".
+
+class Solution(object):
+    def decodeString(self, s):
+        """
+        :type s: str
+        :rtype: str
+        """
+        curr, nums, strs = [], [], []
+        n = 0
+
+        for c in s:
+            if c.isdigit():
+                n = n * 10 + ord(c) - ord('0')
+            elif c == '[':
+                nums.append(n)
+                n = 0
+                strs.append(curr)
+                curr = []
+            elif c == ']':
+                strs[-1].extend(curr * nums.pop())
+                curr = strs.pop()
+            else:
+                curr.append(c)
+
+        return "".join(strs[-1]) if strs else "".join(curr)