LittleElephantAndString | Topcoder Archive

Problem Statement

Little Elephant from the Zoo of Lviv likes strings.

You are given a String A and a String B of the same length. In one turn Little Elephant can choose any character of A and move it to the beginning of the string (i.e., before the first character of A). Return the minimal number of turns needed to transform A into B. If it's impossible, return -1 instead.

Definition

Class:: LittleElephantAndString
Method:: getNumber
Parameters:: String, String
Returns:: int
Method signature:: int getNumber(String A, String B)
(be sure your method is public)

Constraints

A will contain between 1 and 50 characters, inclusive.
B will contain between 1 and 50 characters, inclusive.
A and B will be of the same length.
A and B will consist of uppercase letters ('A'-'Z') only.

Examples

```
"ABC"
```
```
"CBA"
```
```
Returns: 2
```
The optimal solution is to make two turns. On the first turn, choose character 'B' and obtain string "BAC". On the second turn, choose character 'C' and obtain "CBA".
```
"A"
```
```
"B"
```
```
Returns: -1
```
In this case, it's impossible to transform A into B.
```
"AAABBB"
```
```
"BBBAAA"
```
```
Returns: 3
```

"ABCDEFGHIJKLMNOPQRSTUVWXYZ"

"ZYXWVUTSRQPONMLKJIHGFEDCBA"

Returns: 25

```
"A"
```
```
"A"
```
```
Returns: 0
```
```
"DCABA"
```
```
"DACBA"
```
```
Returns: 2
```

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