[LeetCode]String Compression

题目描述：

LeetCode 443. String Compression

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.

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:

1. All characters have an ASCII value in [35, 126].
2. 1 <= len(chars) <= 1000.

题目大意：

对字符串就地压缩

解题思路：

字符串处理

Python代码：

class Solution(object):
    def compress(self, chars):
        """
        :type chars: List[str]
        :rtype: int
        """
        last, n, y = chars[0], 1, 0
        for x in range(1, len(chars)):
            c = chars[x]
            if c == last: n += 1
            else:
                for ch in last + str(n > 1 and n or ''):
                    chars[y] = ch
                    y += 1
                last, n = c, 1
        for ch in last + str(n > 1 and n or ''):
            chars[y] = ch
            y += 1
        while len(chars) > y: chars.pop()
        return y