src/main/java/com/fishercoder/solutions/_443.java

package com.fishercoder.solutions;

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();
        }
    }
}