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# 219.Contains Duplicate II

**219.Contains Duplicate II**

难度:Easy

> Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums\[i] = nums\[j] and the absolute difference between i and j is at most k.

```
Example 1:

Input: nums = [1,2,3,1], k = 3
Output: true
Example 2:

Input: nums = [1,0,1,1], k = 1
Output: true
Example 3:

Input: nums = [1,2,3,1,2,3], k = 2
Output: false
```

新建一个map保存相同元素的索引值，然后比较相同元素索引值中相邻两个索引是否有满足条件的。

```
class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_map<int, vector<int >> cnt;
        for(int i=0;i<nums.size();i++)
            cnt[nums[i]].push_back(i);
        for(auto c:cnt)
            if(c.second.size()>1)
            {
                for(int i=1;i<c.second.size();i++)
                    if(c.second[i]-c.second[i-1]<=k)
                        return true;
                    }
        return false;
    }
};
```

> 执行用时 :56 ms, 在所有 C++ 提交中击败了50.75%的用户\
> 内存消耗 :22 MB, 在所有 C++ 提交中击败了5.03%的用户


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