【2021秋冬】【剑指offer】29. 顺时针打印矩阵

所谓的模拟就是，按想法写出来？
注意定义的上下左右不是长度，是边界

class Solution {
    public int[] spiralOrder(int[][] matrix) {
        if(matrix == null || matrix.length == 0) return new int[0];
        int row = matrix.length, col = matrix[0].length;       
        int[] res = new int[row*col];
        int idx = 0;
        int left = 0, right = col-1;
        int up = 0, down = row-1;
        while(true){
            for(int i=left; i<=right; i++) res[idx++] = matrix[up][i];
            if(++up > down) break;
            for(int i=up; i<=down; i++) res[idx++] = matrix[i][right];
            if(--right < left) break;
            for(int i=right; i>=left; i--) res[idx++] = matrix[down][i];
            if(--down < up) break;
            for(int i=down; i>=up; i--) res[idx++] = matrix[i][left];
            if(++left > right) break;
        }
        return res;
    }
}