Merge pull request #2627 from rmrt1n/287

Create 0287-find-the-duplicate-number.rs

rust/0287-find-the-duplicate-number.rs

@@ -0,0 +1,17 @@
+impl Solution {
+    pub fn find_duplicate(nums: Vec<i32>) -> i32 {
+        let (mut slow, mut fast) = (nums[0], nums[nums[0] as usize]);
+        while slow != fast {
+            slow = nums[slow as usize];
+            fast = nums[nums[fast as usize] as usize];
+        }
+
+        slow = 0;
+        while slow != fast {
+            slow = nums[slow as usize];
+            fast = nums[fast as usize];
+        }
+
+        slow
+    }
+}