Package g0401_0500.s0443_string_compression

Class Solution

  • public class Solution
extends Object
    443 - String Compression.

    Medium

    Given an array of characters chars, compress it using the following algorithm:

    Begin with an empty string s. For each group of consecutive repeating characters in chars:

    • If the group’s length is 1, append the character to s.
    • Otherwise, append the character followed by the group’s length.

    The compressed string s should not be returned separately , but instead, be stored **in the input character array chars **. Note that group lengths that are 10 or longer will be split into multiple characters in chars.

    After you are done modifying the input array , return the new length of the array.

    You must write an algorithm that uses only constant extra space.

    Example 1:

    Input: chars = [“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: The groups are “aa”, “bb”, and “ccc”. This compresses to “a2b2c3”.

    Example 2:

    Input: chars = [“a”]

    Output: Return 1, and the first character of the input array should be: [“a”]

    Explanation: The only group is “a”, which remains uncompressed since it’s a single character.

    Example 3:

    Input: chars = [“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: The groups are “a” and “bbbbbbbbbbbb”. This compresses to “ab12”.

    Example 4:

    Input: chars = [“a”,“a”,“a”,“b”,“b”,“a”,“a”]

    Output: Return 6, and the first 6 characters of the input array should be: [“a”,“3”,“b”,“2”,“a”,“2”].

    Explanation: The groups are “aaa”, “bb”, and “aa”. This compresses to “a3b2a2”. Note that each group is independent even if two groups have the same character.

    Constraints:

    • 1 <= chars.length <= 2000
    • chars[i] is a lowercase English letter, uppercase English letter, digit, or symbol.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • compress

        public int compress​(char[] chars)