# 2090. K Radius Subarray Averages
###### tags: `Leetcode` `Medium` `Prefix Sum`
Link: https://leetcode.com/problems/k-radius-subarray-averages/
## 思路
一定要用long存
求prefix sum然后loop算平均值
## Code

class Solution {
    public int[] getAverages(int[] nums, int k) {
        long[] prefixSum = new long[nums.length];
        prefixSum[0] = nums[0];
        for(int i = 1;i < nums.length;i++){
            prefixSum[i] = prefixSum[i-1]+nums[i];
        }
        int[] ans = new int[nums.length];
        for(int i = 0;i < nums.length;i++){
            ans[i] = -1;
        }
        int center = k;
        if(2*k >= nums.length) return ans;
        for(int end = 2*k;end < nums.length;end++){
            long sum = prefixSum[end] - ((end-2*k-1>=0)?(prefixSum[end-2*k-1]):0);
            ans[center++] = (int)(sum/(long)(2*k+1));
        }
        return ans;
    }
}