using floyd cycle detection: slow & fast pointers

Author: gs146

Find the Duplicate Number

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    int findDuplicate(vector<int>& nums) 
+    {
+        if(nums.empty())       return 0;
+        
+        int slow = nums[0], fast=nums[0];
+        
+        do
+        {
+            slow = nums[slow];
+            fast = nums[nums[fast]];
+        }while(slow!=fast);
+        
+        slow = nums[0];
+        
+        while(fast != slow)
+        {
+            slow=nums[slow];
+            fast=nums[fast];
+        }
+        return fast;
+        
+    }
+};