data structures - How can I make this Algorithm more efficient? -


i've got algorithm produces 2d array containing sum of possible values. example, array [1,5,8,4,5], 2d array sums[1][3] should return sum of index 1-3 in original array (17). believe in terms of big o, efficiency o(n2). there way can make algorithm more efficient? 

public static int[][] sum(int[] values){     int[][] sums = new int[values.length][values.length];     for(int x = 0; x < values.length; x++){         int total = 0;         for(int y = x; y < values.length; y++) {             total += values[y];             sums[x][y] = total;         }     }     return sums; }

you can solve in o(n) time , space prefix-sum array:

array    = [1, 5, 8, 4, 5] prefixes = [1, 6,14,18,23]  sums(1,3) = prefixes[3] - prefixes[0] = 18 - 1 = 17

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