K Radius Subarray Averages.cpp

/* 

    Solution by Rahul Surana
    
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You are given a 0-indexed array nums of n integers, and an integer k.

The k-radius average for a subarray of nums centered at some index i with the radius k is the average of all elements in nums 
between the indices i - k and i + k (inclusive). 
If there are less than k elements before or after the index i, then the k-radius average is -1.

Build and return an array avgs of length n where avgs[i] is the k-radius average for the subarray centered at index i.

The average of x elements is the sum of the x elements divided by x, using integer division. The integer division truncates toward zero, 
which means losing its fractional part.

For example, the average of four elements 2, 3, 1, and 5 is (2 + 3 + 1 + 5) / 4 = 11 / 4 = 2.75, which truncates to 2.
 


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*/


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