剑指 Offer 29. 顺时针打印矩阵

class Solution {
    public int[] spiralOrder(int[][] matrix) {
        //判空
        if(matrix.length == 0){
            return new int[0];
        }
        //定义矩阵 上下左右的边界
        int left = 0;
        int right = matrix[0].length - 1;
        int top = 0;
        int bottom = matrix.length - 1;
        //定义 存放的数组 res，及数组的下标index
        int[] res = new int[(right + 1) * (bottom + 1)];
        int index = 0;
        while(true){
            //从左往右
            for(int i = left;i <= right;i++){
                res[index++] = matrix[top][i];
            }
            if(++top > bottom){
                break;
            }
            //从上往下
            for(int i = top;i <= bottom;i++){
                res[index++] = matrix[i][right];
            }
            if(left > --right){
                break;
            }
            //从右往左
            for(int i = right; i >= left;i--){
                res[index++] = matrix[bottom][i];
            }
            if(top > --bottom){
                break;
            }
            //从下往上
            for(int i = bottom;i >= top; i--){
                res[index++] = matrix[i][left];
            }
            if(++left > right){
                break;
            }
        }
        return res;
    }
}