String Compression

Author: saurabhchris1

String_Compression.py

@@ -0,0 +1,59 @@
+# 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?
+#
+# 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".
+#
+#
+# Input:
+# ["a"]
+#
+# Output:
+# Return 1, and the first 1 characters of the input array should be: ["a"]
+#
+# Explanation:
+# Nothing is replaced.
+#
+#
+# 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
+
+
+class Solution:
+    def compress(self, chars):
+        n = len(chars)
+        i = 0
+        count = 1
+        for j in range(1, n + 1):
+            if j < n and chars[j] == chars[j - 1]:
+                count += 1
+            else:
+                chars[i] = chars[j - 1]
+                i += 1
+                if count > 1:
+                    for d in str(count):
+                        chars[i] = d
+                        i += 1
+                count = 1
+        return i