## 1 Replies - 3014 Views - Last Post: 25 September 2012 - 07:14 AM

### #1 captainhampton Reputation: 14
• Posts: 548
• Joined: 17-October 07

# Determine Bouncy Numbers

Posted 31 December 2011 - 09:47 AM

Description: A more thorough explanation is provided in the comment section above the snippet.
```/*
Author: Vincent Russo

Working from left-to-right if no digit is exceeded by the digit to its left
it is called an increasing number; for example, 134468.

Similarly if no digit is exceeded by the digit to its right it is called a
decreasing number; for example, 66420.

We shall call a positive integer that is neither increasing nor decreasing a
"bouncy" number; for example, 155349.
*/

//Determines if number is "bouncy".
bool isBouncy(string num){

int upCount = 0, downCount = 0;

//Keep track of number form.
for (int i = 0; i < num.length()-1; i++){
if (num[i] <= num[i+1])
upCount++;
if (num[i] >= num[i+1])
downCount++;
}//end for

//If either increasing or decreasing number, it's not bouncy.
if (upCount == num.length()-1 || downCount == num.length()-1)
return false;
return true;
}

int main(){

//Test cases.
string num1 = "155349";
string num2 = "134468";

isBouncy(num1);		//True
isBouncy(num2);		//False

return 0;
}
```

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## Replies To: Determine Bouncy Numbers

### #2 NathanMullenax Reputation: 103
• Posts: 218
• Joined: 23-September 12

## Re: Determine Bouncy Numbers

Posted 25 September 2012 - 07:14 AM

Project Euler? Me too. Still trying to figure out how to get to googol, though. I'm betting there's a closed form expression for the number of bouncy numbers less than 10^n, but I certainly haven't cracked it.

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