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# Time: O(n)
# Space: O(1)
class Solution(object):
def compress(self, chars):
"""
:type chars: List[str]
:rtype: int
"""
anchor, write = 0, 0
for read, c in enumerate(chars):
if read+1 == len(chars) or chars[read+1] != c:
chars[write] = chars[anchor]
write += 1
if read > anchor:
n, left = read-anchor+1, write
while n > 0:
chars[write] = chr(n%10+ord('0'))
write += 1
n /= 10
right = write-1
while left < right:
chars[left], chars[right] = chars[right], chars[left]
left += 1
right -= 1
anchor = read+1
return write