pedrosnk · May 2, 2014 15:02 · May 2, 2014
diff --git a/balance.ex b/balance.ex
@@ -0,0 +1,24 @@
+defmodule Balance do
+  def balance str  do
+    balance(str, 0)
+  end
+  defp balance str, parenthesis_count do
+    if String.length(str) == 0 do
+      parenthesis_count == 0
+    else if parenthesis_count < 0 do
+      false
+    else
+      {head, tail} = String.next_codepoint(str)
+      parenthesis_count_acc = parenthesis_count
+      cond do
+        head == "(" ->
+          parenthesis_count_acc = parenthesis_count_acc + 1
+        head == ")" ->
+          parenthesis_count_acc = parenthesis_count_acc - 1
+        true ->
+      end
+      balance(tail, parenthesis_count_acc)
+    end
+    end
+  end
+end
diff --git a/balance_suite_test.exs b/balance_suite_test.exs
@@ -0,0 +1,20 @@
+defmodule BalanceSuiteTest do
+  use ExUnit.Case
+  import Balance
+
+  test 'balance: "(if (zero? x) max (/ 1 x))" is balanced' do
+    assert balance("(if (zero? x) max (/ 1 x))")
+  end
+
+  test 'balance: "I told him ..." is balanced' do
+    assert balance("I told him ...")
+  end
+
+  test 'balance: ":-)" is unbalanced' do
+    assert !balance(":-)")
+  end
+
+  test 'balance: counting is not enough' do
+    assert !balance("())(")
+  end
+end
diff --git a/count_change.ex b/count_change.ex
@@ -0,0 +1,17 @@
+defmodule CountChange do
+
+  def count_change money, change_list do
+    cond do
+      money == 0 ->
+        1
+      money < 0 ->
+        0
+      length(change_list) == 0 ->
+        0
+      true -> # else
+        [head|tail] = change_list
+        count_change(money - head, change_list) +
+          count_change(money, tail)
+    end
+  end
+end
diff --git a/count_change_test.exs b/count_change_test.exs
@@ -0,0 +1,21 @@
+defmodule CountChangeTest do
+  use ExUnit.Case
+  import CountChange
+
+  test 'countChange: example given in instructions' do
+    assert count_change(4, [1,2]) == 3
+  end
+
+  test 'countChange: sorted CHF' do
+    assert count_change(300, [5,10,20,50,100,200,500]) === 1022
+  end
+
+  test 'countChange: no pennies' do
+    assert count_change(301, [5,10,20,50,100,200,500] ) === 0
+  end
+
+  test('countChange: unsorted CHF') do
+    assert count_change(300, [500,5,50,100,20,200,10]) === 1022
+  end
+
+end
diff --git a/pascal.ex b/pascal.ex
@@ -0,0 +1,11 @@
+defmodule Pascal do
+
+  def pascal column, row do
+    if column == 0 || row == column do
+      1
+    else
+      pascal(column, row - 1) + pascal( column - 1, row - 1 )
+    end
+  end
+
+end
diff --git a/pascal_suite_test.exs b/pascal_suite_test.exs
@@ -0,0 +1,16 @@
+defmodule PascalSuiteTest do
+  use ExUnit.Case
+  import Pascal
+
+  test 'pascal: col=0, row=2' do
+    assert pascal(0,2) == 1
+  end
+
+  test 'pascal: col=1, row=2' do
+    assert pascal(1,2) == 2
+  end
+
+  test 'pascal: col=1, row=3' do
+    assert pascal(1,3) == 3
+  end
+end
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