# Find K Closest Elements Problem

## Description

LeetCode Problem 658.

Given a sorted integer array arr, two integers k and x, return the k closest integers to x in the array. The result should also be sorted in ascending order.

An integer a is closer to x than an integer b if:

•  a - x < b - x , or
•  a - x == b - x and a < b

Example 1:

``````1
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Input: arr = [1,2,3,4,5], k = 4, x = 3
Output: [1,2,3,4]
``````

Example 2:

``````1
2
Input: arr = [1,2,3,4,5], k = 4, x = -1
Output: [1,2,3,4]
``````

Constraints:

• 1 <= k <= arr.length
• 1 <= arr.length <= 10^4
• arr is sorted in ascending order.
• -10^4 <= arr[i], x <= 10^4

## Sample C++ Code

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class Solution {
public:
vector<int> findClosestElements(vector<int>& arr,int k, int x) {
int len = arr.size();
if (len == 0)
return {};

int idx = upper_bound(arr.begin(), arr.end(), x) - arr.begin();
vector<int> ans;
int l = idx - 1, r = idx;
while (k && (l >= 0) && (r <= len-1)) {
k --;
if (arr[r] - x >= x - arr[l]) {
ans.push_back(arr[l--]);
}
else {
ans.push_back(arr[r++]);
}
}
while (k && (l >= 0)) {
k --;
ans.push_back(arr[l--]);
}

while (k && (r <= len - 1)) {
k --;
ans.push_back(arr[r++]);
}
sort(ans.begin(), ans.end());
return ans;
}
};
``````