diff --git a/notes/3. 数组中重复的数字.md b/notes/3. 数组中重复的数字.md
index 6b9366fd..babab09d 100644
--- a/notes/3. 数组中重复的数字.md	
+++ b/notes/3. 数组中重复的数字.md	
@@ -2,7 +2,7 @@
 
 ## 题目链接
 
-[牛客网](https://www.nowcoder.com/practice/623a5ac0ea5b4e5f95552655361ae0a8?tpId=13&tqId=11203&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
+[牛客网](https://www.nowcoder.com/practice/6fe361ede7e54db1b84adc81d09d8524?tpId=13&tqId=11203&tab=answerKey&from=cyc_github)
 
 ## 题目描述
 
@@ -28,19 +28,17 @@ Output:
 
 
 ```java
-public boolean duplicate(int[] nums, int length, int[] duplication) {
-    if (nums == null || length <= 0)
-        return false;
-    for (int i = 0; i < length; i++) {
+public int duplicate(int[] nums) {
+    for (int i = 0; i < nums.length; i++) {
         while (nums[i] != i) {
             if (nums[i] == nums[nums[i]]) {
-                duplication[0] = nums[i];
-                return true;
+                return  nums[i];
             }
             swap(nums, i, nums[i]);
         }
+        swap(nums, i, nums[i]);
     }
-    return false;
+    return -1;
 }
 
 private void swap(int[] nums, int i, int j) {
@@ -48,4 +46,6 @@ private void swap(int[] nums, int i, int j) {
     nums[i] = nums[j];
     nums[j] = t;
 }
+
 ```
+