Create String Compression.py

Author: sugia

String Compression.py

@@ -0,0 +1,74 @@
+'''
+Given an array of characters, compress it in-place.
+
+The length after compression must always be smaller than or equal to the original array.
+
+Every element of the array should be a character (not int) of length 1.
+
+After you are done modifying the input array in-place, return the new length of the array.
+
+
+Follow up:
+Could you solve it using only O(1) extra space?
+
+
+Example 1:
+Input:
+["a","a","b","b","c","c","c"]
+
+Output:
+Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]
+
+Explanation:
+"aa" is replaced by "a2". "bb" is replaced by "b2". "ccc" is replaced by "c3".
+Example 2:
+Input:
+["a"]
+
+Output:
+Return 1, and the first 1 characters of the input array should be: ["a"]
+
+Explanation:
+Nothing is replaced.
+Example 3:
+Input:
+["a","b","b","b","b","b","b","b","b","b","b","b","b"]
+
+Output:
+Return 4, and the first 4 characters of the input array should be: ["a","b","1","2"].
+
+Explanation:
+Since the character "a" does not repeat, it is not compressed. "bbbbbbbbbbbb" is replaced by "b12".
+Notice each digit has it's own entry in the array.
+Note:
+All characters have an ASCII value in [35, 126].
+1 <= len(chars) <= 1000.
+'''
+
+class Solution(object):
+    def compress(self, chars):
+        """
+        :type chars: List[str]
+        :rtype: int
+        """
+        ans = []
+        start = 0
+        end = start
+        while start < len(chars):
+            while end + 1 < len(chars) and chars[end + 1] == chars[start]:
+                end += 1
+            ans.append(chars[start])
+            if end != start:
+                ans += self.getStrArrayFromInt(end - start + 1)
+            start = end + 1
+        
+        for i in xrange(len(ans)):
+            chars[i] = ans[i]
+        return len(ans)
+    
+    def getStrArrayFromInt(self, num):
+        res = []
+        while num > 0:
+            res = [str(num % 10)] + res
+            num //= 10
+        return res