剑指 Offer.29-顺时针打印矩阵

class Solution {
    public int[] spiralOrder(int[][] matrix) {
        // 顺时针打印矩阵(这题至少做了有好多遍了)
        if(matrix == null || matrix.length == 0) return new int[0];
        int top = 0;
        int left = 0;
        int right = matrix[0].length-1;
        int bottom = matrix.length-1;
        int x = 0;
        int[] res = new int[(right+1)*(bottom+1)];
        while(true){
            //从左至右
            for(int i=left;i<=right;i++){
                res[x++] = matrix[top][i];
            }
            if(++top > bottom) break;

            //从上至下
            for(int i=top;i<=bottom;i++){
                res[x++] = matrix[i][right];
            }
            if(--right < left) break;

            //从右至左
            for(int i=right;i>=left;i--){
                res[x++] = matrix[bottom][i];
            }
            if(--bottom < top) break;

            //从下至上
            for(int i=bottom;i>=top;i--){
                res[x++] = matrix[i][left];
            }
            if(++left > right) break;
        }
        return res;
    }
}