update 443

Author: fishercoder1534

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

@@ -2,39 +2,33 @@
 
 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);
+            int i = 0; // Read pointer
+            int res = 0; // Write pointer
+
+            while (i < chars.length) {
+                int j = i;
+                // Advance j to find the end of the repeating group
+                while (j < chars.length && chars[j] == chars[i]) {
+                    j++;
+                }
+
+                // 1. Write the character
+                chars[res++] = chars[i];
+
+                // 2. If the group length is greater than 1, write the count
+                int groupLength = j - i;
+                if (groupLength > 1) {
+                    for (char c : Integer.toString(groupLength).toCharArray()) {
+                        chars[res++] = c;
                     }
-                    prev = chars[i];
-                    count = 1;
                 }
+
+                // 3. Move the read pointer to the start of the next group
+                i = j;
             }
-            sb.append(prev);
-            if (count > 1) {
-                sb.append(count);
-            }
-            int i = 0;
-            for (char c : sb.toString().toCharArray()) {
-                chars[i++] = c;
-            }
-            return sb.length();
+
+            return res;
         }
     }
 }