Update 0287-find-the-duplicate-number.java

Used a do while loop to make the code more concise.

Author: ColstonBod-oy

java/0287-find-the-duplicate-number.java

@@ -3,24 +3,26 @@
 // Space Complexity: O(1)
 
 class Solution {
-
     public int findDuplicate(int[] nums) {
-        int fast = nums[0];
-        int slow = nums[0];
-        boolean first = true;
-        while (first || fast != slow) {
-            if (first) first = false;
+        int slow = 0;
+        int fast = 0;
+
+        do {
             slow = nums[slow];
             fast = nums[nums[fast]];
-            if (fast == slow) break;
         }
-        int slow2 = nums[0];
-        while (slow2 != slow) {
-            if (first) first = false;
-            slow2 = nums[slow2];
+
+        while (slow != fast);
+
+        int slow2 = 0;
+
+        do {
             slow = nums[slow];
-            if (slow2 == slow) return slow;
+            slow2 = nums[slow2];
         }
-        return slow;
+
+        while (slow != slow2);
+
+        return slow2;
     }
 }