Update 287-find-the-duplicate-number.js

Author: everthis

287-find-the-duplicate-number.js

@@ -1,3 +1,28 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const findDuplicate = function(nums) {
+  const len = nums.length
+  if(len > 0) {
+    let slow = nums[0]
+    let fast = nums[nums[0]]
+    while(slow !== fast) {
+      slow = nums[slow]
+      fast = nums[nums[fast]]
+    }
+    slow = 0
+    while(slow !== fast) {
+      slow = nums[slow]
+      fast = nums[fast]
+    }
+    return slow
+  }
+  return -1;
+};
+
+// another
+
 /**
  * @param {number[]} nums
  * @return {number}