一道简单图论题，将二维问题化为两个一维问题，力扣-最佳碰头地点

https://leetcode-cn.com/problems/best-meeting-point/

/* 将问题分解成两个子问题，在一维上最近距离是所有点坐标的中位数，那么分别找到
    x坐标的中位数和y坐标的中位数就是最佳碰头地点
 */
class Solution {
    public int minTotalDistance(int[][] grid) {
        List<Integer> rows = new ArrayList<>();
        List<Integer> cols = new ArrayList<>();

        for (int i = 0; i < grid.length; ++i) {
            for (int j = 0; j < grid[0].length; ++j) {
                if (grid[i][j] == 1) {
                    rows.add(i);
                }
            }
        }

        for (int i = 0; i < grid[0].length; ++i) {
            for (int j = 0; j < grid.length; ++j) {
                if (grid[j][i] == 1) {
                    cols.add(i);
                }
            }
        }

        int x = rows.get(rows.size() / 2);
        int y = cols.get(cols.size() / 2);

        int ans = 0;

        for (int r : rows) {
            ans += Math.abs(x - r);
        }
        for (int c : cols) {
            ans += Math.abs(y - c);
        }

        return ans;
    }
}