半径为k的子数组平均值

class Solution {
public:
    vector<int> getAverages(vector<int>& nums, int k) {
        int n = nums.size();
        vector<int> ans(n, -1);
        if (k * 2 + 1 <= n) {
            long long sum = accumulate(nums.begin(), nums.begin() + k * 2 + 1, 0LL);
            for (int i = k; i + k < n; ++i) {
                if (i != k) {
                    sum += nums[i + k] - nums[i - k - 1];
                }
                ans[i] = sum / (k * 2 + 1);
            }
        }
        return ans;
    }
};

ans(n,-1)这是初始化长度为n的哈希表全部为-1
半径为k子数组的长度是k*2+1
`long long sum = accumulate(nums.begin(), nums.begin() + k * 2 + 1, 0LL);