leetcode443. String Compression
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题目如下:
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
.
解题思路:从头到尾遍历数组,记录连续字符的个数,然后插入数组前部,注意每次插入要记录当前的偏移量offset 。
代码如下:
class Solution(object): def compress(self, chars): """ :type chars: List[str] :rtype: int """ lastChar = None count = 0 inx = 0 offset = 0 chars.append(‘END‘) # terminator while inx < len(chars): i = chars[inx] if lastChar == None: lastChar = i count = 1 elif lastChar == i: count += 1 else: lastOff = offset chars.insert(offset,lastChar) offset += 1 if count != 1: count = str(count) for j in count: chars.insert(offset, j) offset += 1 lastChar = i count = 1 inx += (offset - lastOff) inx += 1 #print chars del chars[-1] return offset
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