Add PHP and Haskell solution

solutions/pete_haskell/coins.hs

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+import Test.Hspec
+import Data.Array
+
+main :: IO ()
+main = hspec $
+    describe "change calculator" $
+        it "should find the minimum number of coins required to reach a target value" $ do
+            minNumCoins [1,2,5] 0 `shouldBe` 0
+            minNumCoins [1,2,5] 1 `shouldBe` 1
+            minNumCoins [1,2,5] 2 `shouldBe` 1
+            minNumCoins [1,2,5] 3 `shouldBe` 2
+            minNumCoins [1,2,5] 4 `shouldBe` 2
+            minNumCoins [1,2,5] 5 `shouldBe` 1
+            minNumCoins [1,2,5] 6 `shouldBe` 2
+            minNumCoins [1,2,5] 7 `shouldBe` 2
+            minNumCoins [1,2,5] 8 `shouldBe` 3
+            minNumCoins [1,2,5] 9 `shouldBe` 3
+            minNumCoins [1,2,5] 10 `shouldBe` 2
+            minNumCoins [1,2,5] 20 `shouldBe` 4
+            minNumCoins [1,2,5] 30 `shouldBe` 6
+            minNumCoins [1,2,5, 10, 20, 50, 100] 999 `shouldBe` 15
+            minNumCoins [1,2,5, 21, 25] 63 `shouldBe` 3
+
+minNumCoins :: [Int] -> Int -> Int
+minNumCoins coins target = lookup ! target
+    where
+        lookup = listArray (0, target) $ map numCoins [0..]
+        numCoins 0 = 0
+        numCoins i | i `elem` coins = 1
+        numCoins i = minimum [1 + lookup ! (i-c) | c <- coins, c < i]

solutions/pete_php/.gitignore

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+vendor

solutions/pete_php/Coin.php

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+<?php
+
+function minNumCoins(array $coins, int $target): int
+{
+    return count(minCoins($coins, $target));
+}
+
+function minCoins(array $coins, int $target): array
+{
+    if ($target <= 0) {
+        return [];
+    }
+    if ($target < min($coins)) {
+        throw new InvalidArgumentException('No coins small enough to make the change!');
+    }
+
+    $minCoinMap = [];
+
+    for ($i = 0; $i <= $target; ++$i) {
+        if (in_array($i, $coins)) {
+            $minCoinMap[$i] = [$i];
+        } else {
+            $smallerCoins = array_filter($coins, function ($coin) use ($i) {
+                return $coin < $i;
+            });
+
+            foreach ($smallerCoins as $c) {
+                $v = $i - $c;
+                if (!array_key_exists($i, $minCoinMap) || count($minCoinMap[$v]) + 1 < count($minCoinMap[$i])) {
+                    $minCoinMap[$i] = array_merge([$c], $minCoinMap[$v]);
+                }
+            }
+        }
+    }
+
+    return $minCoinMap[$target];
+}

solutions/pete_php/CoinTest.php

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+<?php
+require __DIR__ . "/vendor/phpunit/phpunit/src/Framework/Assert/Functions.php";
+require __DIR__ . "/Coin.php";
+
+class CoinTest extends PHPUnit_Framework_TestCase
+{
+    public function test_it_returns_the_minimum_number_of_coins_needed_to_make_change()
+    {
+        $this->isEqual(0, minNumCoins([1, 2, 5], 0));
+        $this->isEqual(1, minNumCoins([1, 2, 5], 1));
+        $this->isEqual(1, minNumCoins([1, 2, 5], 2));
+        $this->isEqual(2, minNumCoins([1, 2, 5], 3));
+        $this->isEqual(2, minNumCoins([1, 2, 5], 4));
+        $this->isEqual(1, minNumCoins([1, 2, 5], 5));
+        $this->isEqual(2, minNumCoins([1, 2, 5], 6));
+        $this->isEqual(2, minNumCoins([1, 2, 5], 7));
+        $this->isEqual(3, minNumCoins([1, 2, 5], 8));
+        $this->isEqual(3, minNumCoins([1, 2, 5], 9));
+        $this->isEqual(2, minNumCoins([1, 2, 5], 10));
+        $this->isEqual(3, minNumCoins([1, 2, 5], 11));
+        $this->isEqual(3, minNumCoins([1, 2, 5], 12));
+        $this->isEqual(4, minNumCoins([1, 2, 5], 13));
+        $this->isEqual(4, minNumCoins([1, 2, 5], 14));
+        $this->isEqual(3, minNumCoins([1, 2, 5], 15));
+        $this->isEqual(5, minNumCoins([1, 2, 5, 10, 20, 50, 100], 256));
+        $this->isEqual(15, minNumCoins([1, 2, 5, 10, 20, 50, 100], 999));
+    }
+
+    public function test_lower_elbonia_coins()
+    {
+        $this->isEqual(3, minNumCoins([1, 2, 5, 10, 21, 25], 24));
+        $this->isEqual(3, minNumCoins([1, 2, 5, 10, 21, 25], 40));
+        $this->isEqual(3, minNumCoins([1, 2, 5, 10, 21, 25], 63));
+        $this->isEqual(8, minNumCoins([1, 2, 5, 10, 21, 25], 158));
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function test_it_throws_an_exception_if_there_is_no_coin_small_enough_to_make_change()
+    {
+        minNumCoins([5, 10], 2);
+    }
+
+    public function test_it_records_the_coins_needed_to_make_change()
+    {
+        $this->isEqual([], minCoins([1, 2, 5], 0));
+        $this->isEqual([1], minCoins([1, 2, 5], 1));
+        $this->isEqual([2], minCoins([1, 2, 5], 2));
+        $this->isEqual([1, 2], minCoins([1, 2, 5], 3));
+        $this->isEqual([2, 2], minCoins([1, 2, 5], 4));
+        $this->isEqual([5], minCoins([1, 2, 5], 5));
+        $this->isEqual([1, 5], minCoins([1, 2, 5], 6));
+        $this->isEqual([5, 2], minCoins([1, 2, 5], 7));
+        $this->isEqual([1, 2, 5], minCoins([1, 2, 5], 8));
+        $this->isEqual([5, 2, 2], minCoins([1, 2, 5], 9));
+        $this->isEqual([5, 5], minCoins([1, 2, 5], 10));
+        $this->isEqual([100, 100, 100, 100, 100, 100, 100, 100, 100, 50, 20, 20, 5, 2, 2], minCoins([1, 2, 5, 10, 20, 50, 100], 999));
+    }
+
+    public function test_it_records_the_lower_elbonia_coins_needed_for_change()
+    {
+        $this->isEqual([21, 2, 1], minCoins([1, 2, 5, 10, 21, 25], 24));
+        $this->isEqual([25, 5, 10], minCoins([1, 2, 5, 10, 21, 25], 40));
+        $this->isEqual([21, 21, 21], minCoins([1, 2, 5, 10, 21, 25], 63));
+        $this->isEqual([25, 25, 25, 25, 25, 21, 10, 2], minCoins([1, 2, 5, 10, 21, 25], 158));
+    }
+
+    private function isEqual($expected, $actual)
+    {
+        return $this->assertEquals($expected, $actual, '', 0.0, 10, true);
+    }
+}

solutions/pete_php/README.md

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+# A solution to the minimum coin/change problem in PHP
+
+Install PHPUnit dependency with composer
+
+```
+$ composer install
+```
+
+Run the tests
+
+```
+$ ./vendor/bin/phpunit CoinTest.php
+```

solutions/pete_php/composer.json

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+{
+    "require-dev": {
+        "phpunit/phpunit": "^5.3"
+    }
+}