From 1e7ce107613c578fdb99d3480e2e04e351434ac6 Mon Sep 17 00:00:00 2001
From: Haidong Ji
Date: Mon, 17 Dec 2018 21:18:43 -0600
Subject: Coin change Dynamic Programming done!

Easy implementation of the algorithm described in course slide. It
helped that I named variables according to the pseudo code. Getting
array indexing right is always a bit tricky so pay attention.---
 .../sources/CoinChangeDynamicProgramming.java      | 29 ++++++++++++++++++++++
 .../tests/CoinChangeDynamicProgrammingTest.java    | 13 ++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 AlgoDesignAndTechniqueEdxJava/sources/CoinChangeDynamicProgramming.java
 create mode 100644 AlgoDesignAndTechniqueEdxJava/tests/CoinChangeDynamicProgrammingTest.java

diff --git a/AlgoDesignAndTechniqueEdxJava/sources/CoinChangeDynamicProgramming.java b/AlgoDesignAndTechniqueEdxJava/sources/CoinChangeDynamicProgramming.java
new file mode 100644
index 0000000..4f3c2b9
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/sources/CoinChangeDynamicProgramming.java
@@ -0,0 +1,29 @@
+import java.util.Scanner;
+
+public class CoinChangeDynamicProgramming {
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        int m = scanner.nextInt();
+        System.out.println(getChange(m));
+    }
+
+    public static int getChange(int money) {
+        // denominations: 1, 3, 4
+        int[] denominations = { 1, 3, 4 };
+        int[] minNumCoins = new int[money + 1];
+        for (int m = 1; m < minNumCoins.length; m++) {
+            minNumCoins[m] = Integer.MAX_VALUE;
+            for (int i = 0; i < denominations.length; i++) {
+                if (m >= denominations[i]) {
+                    int numCoins = minNumCoins[m - denominations[i]] + 1;
+                    if (numCoins < minNumCoins[m]) {
+                        minNumCoins[m] = numCoins;
+                    }
+                }
+            }
+        }
+        return minNumCoins[money];
+    }
+
+}
diff --git a/AlgoDesignAndTechniqueEdxJava/tests/CoinChangeDynamicProgrammingTest.java b/AlgoDesignAndTechniqueEdxJava/tests/CoinChangeDynamicProgrammingTest.java
new file mode 100644
index 0000000..602e013
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/tests/CoinChangeDynamicProgrammingTest.java
@@ -0,0 +1,13 @@
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class CoinChangeDynamicProgrammingTest {
+
+    @Test
+    void test() {
+        assertEquals(2, CoinChangeDynamicProgramming.getChange(2));
+        assertEquals(9, CoinChangeDynamicProgramming.getChange(34));
+    }
+
+}
-- 
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