# Minimum Shelf -Question From Infosys Aspiration 2020 contest in the year 2012 in Java

At a shop of marbles, packs of marbles are prepared. Packets are named A, B, C, D, E ……..
All packets are kept in a VERTICAL SHELF in random order. Any numbers of packets with these names could be kept in that shelf
as in this example: bottom of shelf ---> [AAAJKRDFDEWAAYFYYKK]-----Top of shelf.

All these packets are to be loaded on cars.

The cars are lined in order, so that the packet could be loaded on them. The cars are also named [A, B, C, D, E,………….].

Each Car will load the packet with the same alphabet. So, for example, car ‘A’ will load all the packets with name ‘A’.

The cars will come at the loading point in alphabetical order. So, car ‘B’ will come and take all the packets with name ‘B’ from the shelf, then car ‘C’ will come.

No matter how deep in the shelf any packet ‘B’ is, all of the ‘B’ packets will be displaced before the ‘C’ car arrives.

For that purpose, some additional shelves are provided. The packets which are after the packet B, are kept in those shelves.

Any one of these shelves contains only packets, having the same name. For example, if any particular shelf is used and if a packet with name X is in it, then only the packets having names X will be kept in it. That shelf will look like [XXXXXXX].

If any shelf is used once, then it could be used again only if it is vacant.

Packets from the initial shelf could be unloaded from top only.

Write a program that finds the minimum total number of shelves, including the initial one required for this loading process.
Step 1:
• Implement your logic in function int shelfCount(char* packet)
• char* packet : is the string as packets are kept in the shelf.
• You can create more functions if required, but those functions should be in the same file.

Step 2:
Your solution needs to consider the following constraints.
1. In this problem you have to write a program, that finds the minimum total number of shelves, including the initial one, required for this loading process.
2. The packets are named A, B, C, D, E ……..
3. Any numbers of packets with these names could be kept in the shelf, as in this example: [ZZLLAAJKRDFDDUUGGYFYYKK].
4. All packets are to be loaded on cars. The cars are lined in order, so that the packets could be loaded on them. The cars are also named [A, B, C, D, E,………….].
5. Each Car will load the packets with the same alphabet. So, for example, car ‘A’ will load all the packets with name ‘A’.
6. Each particular car will come at loading point only once. For example, car A will come only once at the loading point.
7. The cars will come at the loading point in alphabetical order. So, car ‘B’ will come and take all the packets with name ‘B’ from the shelf, then car ‘C’ will come.
8. No matter how deep in the shelf any packet ‘B’ is, all of the packets ‘B’ will be displaced before the ‘C’ car arrives.
9. For that purpose, some additional shelves are provided. The packets that are after the packet B, are kept in those shelves.
10. Any one of these shelves contains only packets, having the same name. For example, if any particular shelf is used and if a packet with name S is in it, then only packets having names S will be kept in it. That shelf will look like [SSSSSSS].
11. If any shelf is used once, then it could be used again only if it is vacant.
12. The names of the packets in the shelf should be upper case; otherwise return -1
The Prototype of the function is
int shelfCount(char* packet)
This function takes following arguments.
• packet is the string as packets are kept in the shelf.
• This method returns an integer, which is the minimum number of shelves needed.
Constraints
1. Name of the packets in shelf should be in upper case else return -1.
Example 1
Input
________________________________________
bottom of shelf --->DDDDDD<-----Top of shelf
Output
________________________________________
1

Explanation:
One shelf will be needed because Car A, Car B and Car C will come and go only Car D will come and collect the packet with the initial shelf.
Example 2
Input
________________________________________
ZYXZYXZYXZYX
Output
________________________________________
3
Example 3
Input
________________________________________
ZYXZYmmmXZYXZYX
Output
________________________________________
-1
```package test.minimumshelf;

public class Shelf{

public int shelfCount(String packet)
{
char[] temp=packet.toCharArray();
char chr;
int count=0;
int length=packet.length();
for(int i=0;i<length;i++)

{chr=temp[i];

if(Character.isLowerCase(chr))
{return -1;
}
}
int i=0;
int j;
for(i=0;i<length;i++)

{
if(temp[i]!='\$')
{
for(j=i+1;j<length;j++)
{
if(temp[j]!='\$')
if(temp[i]==temp[j])
{

temp[j]='\$';

}
}

}
else
{continue;
}
}

for(i=0;i<length;i++)
{if(temp[i]!='\$')
{
count=count+1;
}

}

return count;
}

public static void main(String args[])
{
String packet="AABBBCCCDDD";
Shelf a=new Shelf();
int minimumshelf=a.shelfCount(packet);
if(minimumshelf!=-1)
{
System.out.println("Minimum no of shelf"+minimumshelf);
}else
{System.out.println(minimumshelf);
}
}
```