找到长度为n的第一个和最后一个数字，从数字d开始？

Question

I need to find the first and last number with length n and starting with digit d.

For example. i need to find the first and last number with length 6 and starting in 2 The result should be first number=200000 and last number=299999 .

I there any functions available in php to help me to get a logic to solve this.??

Hope Someone can help me..

Answer 1

You could try relying on the fact that the smallest number will end in all 0's and the largest in all 9's, and then use str_repeat to generate the appropriate tailing digits:

echo $d . str_repeat('0', $n-1);
echo $d . str_repeat('9', $n-1);

For $d = 2 and $n = 6, this will give you 200000 and 299999.

If you need them as integers, just do

$start = (int)($d . str_repeat('0', $n-1));
$finish = (int)($d . str_repeat('9', $n-1));
var_dump($start);
var_dump($finish);

Output:

int(200000)
int(299999)