CoinFlipsDiv2 | Topcoder Archive

Problem Statement

You have n coins, labeled 0 through n-1. Each of the coins shows either heads or tails. You are given the states of all coins in the String state with n characters. For each i, state[i] is 'H' if coin i shows heads, or 'T' if it shows tails.

The coins are laid out in a row, ordered from coin 0 to coin n-1. A coin is called interesting if it differs from at least one of its neighbors. (For example, a coin that shows heads is interesting if at least one of its neighbors shows tails.) Return the number of interesting coins.

Definition

Class:: CoinFlipsDiv2
Method:: countCoins
Parameters:: String
Returns:: int
Method signature:: int countCoins(String state)
(be sure your method is public)

Notes

The value of n is not given explicitly. Instead, you can determine it as the number of characters in state.

Constraints

state will have between 1 and 50 elements, inclusive.
Each character of state will be either 'H' or 'T'.

Examples

```
"HT"
```
```
Returns: 2
```
Coin 0 is interesting because it shows heads and its only neighbor shows tails. Similarly, coin 1 is interesting because it shows tails and its only neighbor shows heads. Thus, the answer is 2.
```
"T"
```
```
Returns: 0
```
In this test case there is a single coin. It has no neighbors, and therefore it has no different neighbors. This means that the coin is not interesting.
```
"HHH"
```
```
Returns: 0
```
None of these coins are interesting, because each of them is only adjacent to coins that show the same side.
```
"HHTHHH"
```
```
Returns: 3
```
Here, the three interesting coins are coins 1, 2, and 3. (Remember that the indices are 0-based.)
```
"HHHTTTHHHTTTHTHTH"
```
```
Returns: 12
```

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