import java.util.*;
public class Solution {
    public ArrayList<Integer> printMatrix(int[][] matrix) {
        ArrayList<Integer> res=new ArrayList<>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
            return res;
        int n=matrix.length;
        int m=matrix[0].length;
        int r1=0,r2=n-1;
        int c1=0,c2=m-1;
        while (r1<=r2&&c1<=c2){
            for(int i=c1;i<=c2;i++){
                res.add(matrix[r1][i]);
            }
            for(int i=r1+1;i<=r2;i++){
                res.add(matrix[i][c2]);
            }
            if(r2>r1){
                for(int i=c2-1;i>=c1;i--){
                    res.add(matrix[r2][i]);
                }
            }
            if(c2>c1){
                for(int i=r2-1;i>r1;i--){
                   res.add(matrix[i][c1]);
                }
            }
            r1++;
            r2--;
            c1++;
            c2--;
        }
        return res;
    }
}