diff options
| -rw-r--r-- | Scala/recfun/src/main/scala/recfun/Main.scala | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/Scala/recfun/src/main/scala/recfun/Main.scala b/Scala/recfun/src/main/scala/recfun/Main.scala index 277aa1a..b8ac271 100644 --- a/Scala/recfun/src/main/scala/recfun/Main.scala +++ b/Scala/recfun/src/main/scala/recfun/Main.scala @@ -14,15 +14,32 @@ object Main { /** * Exercise 1 */ - def pascal(c: Int, r: Int): Int = ??? + def pascal(c: Int, r: Int): Int = + if (c == 0 || c == r) 1 else pascal(c-1, r-1) + pascal(c, r-1) /** * Exercise 2 */ - def balance(chars: List[Char]): Boolean = ??? + def balance(chars: List[Char]): Boolean = { + def balanceR(chars: List[Char], depth: Int): Boolean = + if (chars.isEmpty) depth == 0 + else if (chars.head == '(') balanceR(chars.tail, depth + 1) + else if (chars.head == ')') { + if (depth == 0) false + else balanceR(chars.tail, depth - 1) + } + else balanceR(chars.tail, depth) + balanceR(chars, 0) + } /** * Exercise 3 */ - def countChange(money: Int, coins: List[Int]): Int = ??? + def countChange(money: Int, coins: List[Int]): Int = { + if (money == 0) 1 // successful recursion + else if (money < 0) 0 // too far + else if (coins.isEmpty) 0 // no more coins + // use this coin (one more time) or not anymore + else countChange(money - coins.head, coins) + countChange(money, coins.tail) + } } |