Update 数组相关.md

blogs/Algorithm/剑指 Offer/数组相关.md

@@ -2,6 +2,21 @@
 数组相关
 ---
 
+[03. 数组中重复的数字](https://leetcode-cn.com/problems/shu-zu-zhong-zhong-fu-de-shu-zi-lcof/)
+
+```java
+class Solution {
+    public int findRepeatNumber(int[] nums) {
+        int[] res = new int[nums.length];
+        for (int i : nums) {
+            res[i]++;
+            if (res[i] > 1) return i;
+        }
+        return -1;
+    }
+}
+```
+
 [04. 二维数组中的查找](https://leetcode-cn.com/problems/er-wei-shu-zu-zhong-de-cha-zhao-lcof/)
 
 ```java