Some interview questions for Jumei today

1. Write a function to randomly place 1,2,3,4,5,6 into an array. 3 cannot be in the third position, and 5 and 6 cannot be next to each other.

function sort_test($array)
{
    while(true) {
        shuffle($array);
        $temp = array_flip($array);
        if ($array[2] != 3 && 1 != abs($temp[5] - $temp[6])) {
            return $array;
        }
    }
}
$array = array(1,2,3,4,5,6);
print_r(sort_test($array));

2. Write a function to implement the first letter that appears once in the string $str="asdfasflasdfopafdsa".

function get_target_letter($str)
{
    $i = 0;
    $array = array();
    while(isset($str[$i])) {
        $array[$str[$i]] = isset($array[$str[$i]]) ? $array[$str[$i]] + 1 : 1;
        $i ++;
    }
    foreach($array as $key=>$val) {
        if ($val == 1) {
            return $key;
        }
    }
    return false;
}
echo get_target_letter('asdfastflasdfopafdsa');

3. There are two tables:

CREATE TABLE products (
  product_id INT UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
  product_name VARCHAR(64) NOT NULL
);
CREATE TABLE orders (
  product_id INT UNSIGNED NOT NULL ,
  create_at INT UNSIGNED NOT NULL,
  num INT UNSIGNED NOT NULL 
);

Please write a SQL statement to query the product name and total sales volume during the t1-t2 time period and sort them from high to low according to the total sales volume.

My approach:

SELECT
  products.product_name,
  number.num
FROM ((SELECT
         product_id,
         sum(num) AS num
       FROM orders
         WHERE orders.create_at BETWEEN {$t1} AND {$t2}
       GROUP BY product_id) AS number) INNER JOIN products ON products.product_id = number.product_id
ORDER BY number.num DESC;

These three questions are more impressive. I can’t remember the others. The answers are written according to my own approach. Please correct me if I’m wrong

The above introduces several interview questions at Jumei today, including relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.