# leetcode\_219

## 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
```

## Solutions

1. **hashmap**
2. we can remove items in hasmap added before `i - k` to save space.

```cpp
class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_set<int> s;
        for (int i = 0; i < nums.size(); i++) {
            if (i > k) s.erase(nums[i - k - 1]);  /*   remove elements to save space */
            if (!s.insert(nums[i]).second) return true;
        }
        return false;
    }
};
```