题解 | #螺旋矩阵#

左到右 结束时 ++top>bottom 迭代终止

上到下 结束时 --right<left 迭代终止

右到左 结束时 top>--bottom 迭代终止

下到上 结束时 ++left>right 迭代终止

public class Solution {
    public ArrayList<Integer> spiralOrder(int[][] matrix) {
        ArrayList<Integer> res = new  ArrayList<>();
        int len = matrix.length;
        if (matrix == null || len == 0){
            return  res;
        }
        int left = 0;
        int right = matrix[0].length-1;
        int top = 0;
        int bottom = matrix.length-1;
        while (true){

            for (int i = left; i <=right ; i++) {
                int val = matrix[top][i];
                res.add(val);
            }
            if (++top>bottom) break;

            for (int i = top; i <=bottom ; i++) {
                int val = matrix[i][right];
                res.add(val);
            }
            if (--right<left)break;

            for (int i = right; i >=left ; i--) {
                int val = matrix[bottom][i];
                res.add(val);
            }
            if (top>--bottom) break;

            for (int i = bottom; i >=top ; i--) {
                int val = matrix[i][left];
                res.add(val);
            }
            if (++left>right) break;
        }
        return  res;
    }
}