K Radius Subarray Averages LeetCode solution in Java

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class Solution {
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  public int[] getAverages(int[] nums, int k) {
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    if (k == 0) return nums;
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    int N = nums.length;
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    long[] sum = new long[N];
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    sum[0] = nums[0];
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    for (int i = 1; i < N; i++) sum[i] = sum[i - 1] + nums[i]; // Sum of 0 - ith element at sum[i]
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    int[] ret = new int[N];
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    Arrays.fill(ret, -1);
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    for (int i = k; i < N - k; i++) // Beyond this range, there are less than k elements so -1
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    {
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      long temp = (sum[i + k] - sum[i - k] + nums[i - k]) / (k * 2 + 1);
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      ret[i] = (int) temp;
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    }
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    return ret;
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  }
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}