From 1526892aba71df044a1e50ba2f9aae06d56c7071 Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 15 Mar 2021 17:14:55 +0000
Subject: [PATCH 1/6] Solution to Project Euler problem 31

---
 ProjectEuler/Problem31.java | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 ProjectEuler/Problem31.java

diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
new file mode 100644
index 000000000000..6f58ddbebe5d
--- /dev/null
+++ b/ProjectEuler/Problem31.java
@@ -0,0 +1,36 @@
+package ProjectEuler;
+
+/**
+ * In the United Kingdom the currency is made up of pound (£) and pence (p). There are eight coins
+ * in general circulation:
+ *
+ * <p>1p, 2p, 5p, 10p, 20p, 50p, £1 (100p), and £2 (200p).
+ *
+ * <p>It is possible to make £2 in the following way:
+ *
+ * <p>1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p
+ *
+ * <p>How many different ways can £2 be made using any number of coins?
+ *
+ * <p>link: https://projecteuler.net/problem=31
+ */
+public class Problem31 {
+  public static void main(String[] args) {
+    assert solution1() == 1;
+  }
+
+  public static int solution1() {
+    int target = 200;
+    int[] coins = {1, 2, 5, 10, 20, 50, 100, 200};
+    int[] combos = new int[201];
+    combos[0] = 1;
+
+    for (int coin : coins) {
+      for (int j = coin; j <= target; j++) {
+        combos[j] += combos[j - coin];
+      }
+    }
+
+    return combos[200];
+  }
+}

From c82a282f74714777924f966c3707b786e172ccf8 Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 15 Mar 2021 20:12:23 +0000
Subject: [PATCH 2/6] Changed assert to correct value

---
 ProjectEuler/Problem31.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
index 6f58ddbebe5d..22fc709d9944 100644
--- a/ProjectEuler/Problem31.java
+++ b/ProjectEuler/Problem31.java
@@ -16,7 +16,7 @@
  */
 public class Problem31 {
   public static void main(String[] args) {
-    assert solution1() == 1;
+    assert solution1() == 73682;
   }
 
   public static int solution1() {

From ca5fa17d2e4a132a25435cb9eff5a4df271ea092 Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 15 Mar 2021 20:39:43 +0000
Subject: [PATCH 3/6] Recommitting to see if checks run properly

---
 ProjectEuler/Problem31.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
index 22fc709d9944..ed8bf3e071fa 100644
--- a/ProjectEuler/Problem31.java
+++ b/ProjectEuler/Problem31.java
@@ -12,7 +12,7 @@
  *
  * <p>How many different ways can £2 be made using any number of coins?
  *
- * <p>link: https://projecteuler.net/problem=31
+ * <p> link: https://projecteuler.net/problem=31
  */
 public class Problem31 {
   public static void main(String[] args) {

From aef3fe446365a9a12c9d801ae06a7efd27d4570e Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 15 Mar 2021 21:29:27 +0000
Subject: [PATCH 4/6] Fixed formatting

---
 ProjectEuler/Problem31.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
index ed8bf3e071fa..22fc709d9944 100644
--- a/ProjectEuler/Problem31.java
+++ b/ProjectEuler/Problem31.java
@@ -12,7 +12,7 @@
  *
  * <p>How many different ways can £2 be made using any number of coins?
  *
- * <p> link: https://projecteuler.net/problem=31
+ * <p>link: https://projecteuler.net/problem=31
  */
 public class Problem31 {
   public static void main(String[] args) {

From e2a0adbef44f225bf96f54502057c4bd11284136 Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 15 Mar 2021 23:29:01 +0000
Subject: [PATCH 5/6] All checks didn't run last time

---
 ProjectEuler/Problem31.java | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
index 22fc709d9944..8efef70222b3 100644
--- a/ProjectEuler/Problem31.java
+++ b/ProjectEuler/Problem31.java
@@ -16,18 +16,18 @@
  */
 public class Problem31 {
   public static void main(String[] args) {
-    assert solution1() == 73682;
+    assert solution() == 73682;
   }
 
-  public static int solution1() {
+  public static int solution() {
     int target = 200;
     int[] coins = {1, 2, 5, 10, 20, 50, 100, 200};
     int[] combos = new int[201];
     combos[0] = 1;
 
     for (int coin : coins) {
-      for (int j = coin; j <= target; j++) {
-        combos[j] += combos[j - coin];
+      for (int i = coin; i <= target; i++) {
+        combos[i] += combos[i - coin];
       }
     }
 

From c2bfb4d114773f1a96117d00751349d6d7c12f2c Mon Sep 17 00:00:00 2001
From: daniel-campbell-327
 <63069027+daniel-campbell-327@users.noreply.github.com>
Date: Mon, 29 Mar 2021 15:22:38 +0100
Subject: [PATCH 6/6] Added Problem 19

---
 ProjectEuler/Problem19.java | 46 +++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 ProjectEuler/Problem19.java

diff --git a/ProjectEuler/Problem19.java b/ProjectEuler/Problem19.java
new file mode 100644
index 000000000000..0dab323a9029
--- /dev/null
+++ b/ProjectEuler/Problem19.java
@@ -0,0 +1,46 @@
+package ProjectEuler;
+
+import java.util.Arrays;
+
+public class Problem19 {
+  public static void main(String[] args) {
+    assert solution() == 171;
+  }
+
+  public static int solution() {
+    int year = 1901;
+    boolean leapYear = false;
+    int totalSundays = 0;
+    int currentDay = 2; // start on a monday
+
+    while (year <= 2000) {
+      leapYear = false;
+      if (year % 4 == 0) {
+        if (year % 100 == 0 && year % 400 == 0) {
+          leapYear = true;
+        } else leapYear = year % 100 != 0 || year % 400 == 0;
+      }
+
+      for (int month = 1; month <= 12; month++) {
+        if (currentDay == 7) {
+          totalSundays++;
+        }
+        if (Arrays.asList(1, 3, 5, 7, 8, 10, 12).contains(month)) {
+          currentDay += 3;
+        } else if (Arrays.asList(4, 6, 9, 11).contains(month)) {
+          currentDay += 2;
+        } else if (leapYear) {
+          currentDay += 1;
+        }
+
+        if (currentDay > 7) {
+          currentDay -= 7;
+        }
+      }
+
+      year++;
+    }
+
+    return totalSundays;
+  }
+}