Interview questions, not done

food0012

I do not understand the meaning

别叫我女生

Specify as a number, such as 1 2 3, I only need 3 digits which is 123 132 213 231 312 321
For example 1 2 I only need 2 digits is 12 21
Give a few digits

ly_1112

Provide an idea, find the smallest (such as 123) and the largest (such as 321) in the number combination, and then output the number between them

dommionr

Arrange them all,
Minimum and maximum, as long as the largest is selected each time is the largest, the smallest is selected the smallest is the smallest

44964869

import java.io. *;

public class Test {

public static void main (String [] args) throws Exception
{
Ranch
FileWriter out = new FileWriter ("result.txt");
int count = 0;
for (int i = 123; i <= 321; i ++)
{
String s = new String (i + ",");
if (s.indexOf ("4")> = 0)
{
continue;
}
else if (s.indexOf ("5")> = 0)
{
continue;
}
else if (s.indexOf ("6")> = 0)
{
continue;
}
else if (s.indexOf ("7")> = 0)
{
continue;
}
else if (s.indexOf ("8")> = 0)
{
continue;
}
else if (s.indexOf ("9")> = 0)
{
continue;
}
else if (s.indexOf ("0")> = 0)
{
continue;
}
else
{
count ++;
out.write (s, 0, s.length ());
}
}
System.out.println ("find:" + count);
out.close ();
}
}

nanase

The procedure is for someone else.

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

public class Test
{
    public static void main (String [] args) throws Exception
    {
String [] array = new String [] {"1", "2", "3"};
listAll (Arrays.asList (array), "");
    }

    public static void listAll (List candidate, String prefix)
    {
if (prefix.length () == 3)
{
System.out.println (prefix);
}
Ranch
for (int i = 0; i <candidate.size (); i ++)
{
List temp = new LinkedList (candidate);
listAll (temp, prefix + temp.remove (i));
}
    }
}

Take 3 digits as an example, set the list of elements to be retrieved to, and to display String as prefix
First traverse to fetch dates from candidate and add to prefix, one less for candidate and one more for prefix
In this way, recursive loops are the best choice.

hushengfox

Bangding

The purpose of the question is to output several permutations and combinations, and then the fourth digit of each combination is not necessary?

kevinak123

ret + = s [i];
getOne (ret, pos + 1);
ret = ret.substring (0, pos-1);
The control logic is here, if you want to do special processing for some bits, do it here
You can draw a trick for each function call, knowing its internal principles, you can modify it arbitrarily.

skyslasher

Study! ~~~

别叫我女生

Thank you, let me see