Create 217. Contains Duplicate.md

217. Contains Duplicate.md

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+# [217. Contains Duplicate](https://leetcode.com/problems/contains-duplicate/description/)
+# 思路
+先对数组进行排序，排序后重复的数一定是相邻的，再遍历一遍即可。
+# C++
+```
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        for(int i = 1; i < nums.size(); i++)
+            if(nums[i] == nums[i-1]) return true;
+        return false;
+    }
+};
+```