[LC] 443. String Compression

Posted 2021-03-16 xuanlu

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".

class Solution {
    public int compress(char[] chars) {
        if (chars.length <= 1) {
            return chars.length; 
        }
        int index = 0;
        int res = 0;
        while (index < chars.length) {
            int curCount = 0;
            char curChar = chars[index];
            while (index < chars.length && chars[index] == curChar) {
                index += 1;
                curCount += 1;
            }
            chars[res++] = curChar;
            if (curCount != 1) {
                for (char c: Integer.toString(curCount).toCharArray()) {
                    chars[res] = c;
                    res += 1;
                }
            }
        }
        return res;
    }
}