2月1日报

empty 2d array: new int[0][];
“tt”
import static java.lang.System.*

floor() 对一个数向下取整

1030 Matrix Cells in Distance Order
格式为: Arrays.sort(target, (s1, s2) -> {expression});

class Solution {
    public int[][] allCellsDistOrder(int rows, int cols, int rCenter, int cCenter) {
        int[][] res = new int[rows*cols][2];
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                int index = i*cols + j;
                res[index][0] = i;
                res[index][1] = j;
            }
        }

        Arrays.sort(res, (arr1, arr2) -> {
        int dis1 = dis(arr1[0], arr1[1], rCenter, cCenter);
        int dis2 = dis(arr2[0], arr2[1], rCenter, cCenter);
        return Integer.compare(dis1, dis2);}
        );

        return res;
    }

    private int dis (int x1, int y1, int x2, int y2) {
        return Math.abs(x1-x2) + Math.abs(y1-y2);
    }
}

MinPQ in java