2090. K Radius Subarray Averages

class Solution {
public:
    vector<int> getAverages(vector<int>& nums, int k) {

         int n=nums.size();
         vector<long long int> pre(n),suff(n);

         pre[0]=nums[0];
         for(int i=1;i<n;i++)
            pre[i]=pre[i-1]+nums[i];
        
 
        suff[n-1]=nums[n-1];
        for(int i=n-2;i>=0;i--)
            suff[i]=suff[i+1]+nums[i];
        
 
        vector<int> ans;

        for(int i=0;i<n;++i){

            if(i-k<0 || i+k>=n)
                ans.push_back(-1);
            
 
            else{

           long long int sum = (long long int)((suff[i-k]-suff[i]) + (pre[i+k]-pre[i]) + nums[i]);
                sum=sum/(2*k+1);
                ans.push_back(sum);
            }
        }
 
        return ans;
    }
};