compress.py

#    -*-    coding: utf-8    -*-
'''
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.
'''
"""
        :type chars: List[str]
        :rtype: int
        """
class Solution:
    def compress(self, chars):
        if len(chars) == 1:
            return 1
        res = []
        i = 1
        idx = 0
        while i < len(chars):
            cnt = 1
            f = 0
            res.append(chars[idx])
            while i < len(chars) and chars[i] == chars[idx]:
                cnt += 1
                i += 1
            
            if cnt < 10 and cnt > 1:
                res.append(str(cnt))
            elif cnt == 1:
                f = 1
            else:
                tmp = []
                while cnt != 0:
                    tmp.append(str(cnt%10))
                    cnt = cnt//10
                for j in range(len(tmp)-1, -1, -1):
                    res.append(tmp[j])
            idx = i
            i += 1
        if chars[-1] != chars[-2]:
            res.append(chars[idx])
        for i in range(len(res)):
            chars[i] = res[i]
        return len(res)

if __name__ == "__main__":
	sol = Solution()
	chars = ["a","b","b","c"]
	print(sol.compress(chars))