LeetCode 1878: Get Biggest Three Rhombus Sums in a Grid Solution

Master LeetCode problem 1878 (Get Biggest Three Rhombus Sums in a Grid), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1878. Get Biggest Three Rhombus Sums in a Grid

Medium

Array Math Sorting Heap (Priority Queue)Matrix Prefix Sum

Problem Explanation

Explanation

To solve this problem, we can iterate through all possible rhombus shapes in the grid and calculate their sums. We can achieve this by fixing the center of the rhombus and varying the radius to form the rhombus shape. For each rhombus, we calculate its sum by summing the values of the border elements. We then store the unique rhombus sums in a set and finally return the top three distinct sums in descending order.

Time complexity: O(mnmin(m,n)) where m is the number of rows and n is the number of columns in the grid
Space complexity: O(m*n)

Solution Code

import java.util.*;

class Solution {
    public int[] getBiggestThree(int[][] grid) {
        int m = grid.length;
        int n = grid[0].length;
        Set<Integer> rhombusSums = new HashSet<>();

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                rhombusSums.add(grid[i][j]);

                for (int r = 1; i + r < m && i - r >= 0 && j + 2 * r < n; r++) {
                    int sum = 0;
                    for (int k = 0; k < r; k++) {
                        sum += grid[i - k][j + k] + grid[i + k][j + k] + grid[i - k][j + 2 * r - k] + grid[i + k][j + 2 * r - k];
                    }
                    rhombusSums.add(sum);
                }
            }
        }

        List<Integer> uniqueSums = new ArrayList<>(rhombusSums);
        Collections.sort(uniqueSums, Collections.reverseOrder());

        return uniqueSums.stream().limit(3).mapToInt(Integer::intValue).toArray();
    }
}

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