【剑指offer】19：顺时针打印矩阵

function printMatrix(matrix)
{
    // write code here
    if (matrix == 0 || matrix.length == 0) {
        return matrix;
    }
    var res = [];
    var top = 0, left = 0,
        bottom = matrix.length - 1,
        right = matrix[0].length - 1;
    while (top <= bottom && left <= right) {  //循环一圈
        //从左上到右上
        for (let i = left; i <= right; i++) {
            res.push(matrix[top][i]);
        }
        //从右上到右下
        for (let i = top + 1; i <= bottom; i++){
            res.push(matrix[i][right]);
        }
        //从右下到左下
        if (bottom !== top) {
            for (let i = right - 1; i >= left; i--) {
                res.push(matrix[bottom][i]);
            }
        }
        //从左下到左上
        if (left !== right) {
            for (let i = bottom - 1; i >= top + 1; i--) {
                res.push(matrix[i][left]);
            }
        }
        top++;
        left++;
        bottom--;
        right--;
    }
    return res;
}