_443.java

package com.fishercoder.solutions;

/**
 * 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:
 All characters have an ASCII value in [35, 126].
 1 <= len(chars) <= 1000.
 */
public class _443 {
    public static class Solution1 {
        /**This is breaking the rules, it's not in-place.*/
        public int compress(char[] chars) {
            if (chars == null || chars.length == 0) {
                return 0;
            }
            StringBuilder sb = new StringBuilder();
            int count = 1;
            char prev = chars[0];
            for (int i = 1; i < chars.length; i++) {
                if (chars[i] == prev) {
                    count++;
                } else {
                    if (count > 1) {
                        sb.append(prev);
                        sb.append(count);
                    } else if (count == 1) {
                        sb.append(prev);
                    }
                    prev = chars[i];
                    count = 1;
                }
            }
            sb.append(prev);
            if (count > 1) {
                sb.append(count);
            }
            int i = 0;
            for (char c : sb.toString().toCharArray()) {
                chars[i++] = c;
            }
            return sb.length();
        }
    }
}