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+# [219. Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/description/)
+# 思路
+判断数组是否有重复元素，而且重复元素下标差的绝对值不大于k，首先简单的思路就是用map，这里给出另一种解法:  
+定义一个结构体num_with_index记录数组元素的值和下标，然后再对结构体按照值进行排序，排序后重复元素肯定相邻，再判断下标是否满足条件即可。
+# C++
+```
+class Solution {
+    struct num_with_index{
+        int num;
+        int index;
+    };
+public:
+    // 这里必须加static否则编译不过，原因参考https://www.cnblogs.com/scoyer/p/6533685.html
+    static bool mycompare(const num_with_index &a, const num_with_index &b){
+        return a.num > b.num;
+    }
+    bool containsNearbyDuplicate(vector<int>& nums, int k) {
+        vector<num_with_index>newnums;
+        num_with_index newnum;
+        for(int i = 0; i < nums.size(); i++){
+            newnum.num = nums[i];
+            newnum.index = i;
+            newnums.push_back(newnum);
+        }
+        sort(newnums.begin(), newnums.end(), mycompare);
+        for(int i = 1; i < nums.size(); i++)
+            if(newnums[i].num == newnums[i-1].num && abs(newnums[i].index - newnums[i-1].index) <= k) return true;
+        return false;
+    }
+};
+```