/** direction 0 代表向右, 1 代表向下, 2 代表向左, 3 代表向上*/publicList<Integer>spiralOrder(int[][] matrix) {
List<Integer>ans=newArrayList<>();
if(matrix.length==0){
returnans;
    }
intstart_x=0, 
start_y=0,
direction=0, 
top_border=-1,  //上边界right_border=matrix[0].length,  //右边界bottom_border=matrix.length, //下边界left_border=-1; //左边界while(true){
//全部遍历完结束if (ans.size() ==matrix.length*matrix[0].length) {
returnans;
        }
//注意 y 方向写在前边，x 方向写在后边ans.add(matrix[start_y][start_x]);
switch (direction) {
//当前向右case0:
//继续向右是否到达边界//到达边界就改变方向，并且更新上边界if (start_x+1==right_border) {
direction=1;
start_y+=1;
top_border+=1;
                } else {
start_x+=1;
                }
break;
//当前向下case1:
//继续向下是否到达边界//到达边界就改变方向，并且更新右边界if (start_y+1==bottom_border) {
direction=2;
start_x-=1;
right_border-=1;
                } else {
start_y+=1;
                }
break;
case2:
if (start_x-1==left_border) {
direction=3;
start_y-=1;
bottom_border-=1;
                } else {
start_x-=1;
                }
break;
case3:
if (start_y-1==top_border) {
direction=0;
start_x+=1;
left_border+=1;
                } else {
start_y-=1;
                }
break;
        }
    }
}