DigitsSwap | Topcoder Archive

Problem Statement

You are given two positive integers, x and y, whose decimal representations contain the same number of digits. A digit-swap operation for an index i swaps the digits at the i-th positions in x and y. After exactly swaps digit-swap operations, what is the maximal possible value of x*y? Return the String representation of this maximal product with no leading zeroes.

Definition

Class:: DigitsSwap
Method:: maximalProduct
Parameters:: String, String, int
Returns:: String
Method signature:: String maximalProduct(String x, String y, int swaps)
(be sure your method is public)

Constraints

x and y will each contain between 1 and 50 characters, inclusive.
x and y will contain only decimal digits ('0' to '9'), and will not start with a '0'.
x and y will contain the same number of characters.
swaps will be between 0 and 1,000,000,000, inclusive.

Examples

```
"123"
```
```
"321"
```
```
2
```
```
Returns: "39483"
```
You can transform the numbers to "123", "321" (making two swaps at the same position) or to "321", "123" (making swaps at positions 0 and 2) to produce the product 39483.
```
"4531"
```
```
"1332"
```
```
0
```
```
Returns: "6035292"
```
You are not allowed to make swaps, so the answer is just x * y.
```
"13425"
```
```
"87694"
```
```
99
```
```
Returns: "1476187680"
```
The optimal answer is 17695 * 83424.

"2872876342876443222"

"2309482482304823423"

Returns: "6669566046086333877050194232995188906"

"940948"

"124551"

Returns: "133434353148"

"56710852"

"18058360"

Returns: "1050671725722720"

```
"9"
```
```
"1"
```
```
1000000000
```
```
Returns: "9"
```

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