Adding comments

src/main/java/simulate_diplomacy/SimulateDiplomacy.java

@@ -0,0 +1,171 @@
+package simulate_diplomacy;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SimulateDiplomacy {
+
+	public static class Army implements Comparable<Army> {
+		String name;
+		String location;
+		int strength;
+
+		Army(String n, String l) {
+			this.name = n;
+			this.location = l;
+			this.strength = 1;
+		}
+
+		@Override
+		public int compareTo(Army a) {
+			return name.compareTo(a.name);
+		}
+
+		@Override
+		public String toString() {
+			return name + " " + (strength == 0 ? "[dead]" : location);
+		}
+	}
+
+	public static class Solution {
+
+		List<String> play(List<String> actions) {
+			List<Army> armies = new ArrayList<>();
+			Map<String, Army> indexes = new HashMap<>();
+			List<String[]> supports = new ArrayList<>();
+			for (String action : actions) {
+				String[] tokens = action.split(" ");
+				String name = tokens[0];
+				String location = tokens[1];
+				Army a = indexes.get(name);
+				if (a == null) {
+					a = new Army(name, location);
+					armies.add(a);
+					indexes.put(a.name, a);
+				}
+				String act = tokens[2];
+				switch (act) {
+					case "Move":
+						a.location = tokens[3];
+						break;
+					case "Support":
+						supports.add(new String[] { a.name, tokens[3] });
+						break;
+				}
+			}
+
+			Map<String, List<Army>> attacks = new HashMap<>();
+			for (Army a : armies) {
+				attacks.compute(a.location, (s, list) -> {
+					if (list == null)
+						list = new ArrayList<>();
+					list.add(a);
+					return list;
+				});
+			}
+			// Deal with the attacks
+			for (Map.Entry<String, List<Army>> e : attacks.entrySet()) {
+				List<Army> list = e.getValue();
+				if (list.size() > 1) {
+					for (Army a : list) {
+						a.strength = 0;
+					}
+				}
+			}
+			// Deal with the support, especially the case where the armies receive more than one support
+			for (String[] sup : supports) {
+				String s1 = sup[0];
+				String s2 = sup[1];
+				Army a1 = indexes.get(s1);
+				Army a2 = indexes.get(s2);
+				if (a1.strength > 0) {
+					a2.strength++;
+				}
+			}
+			for (Map.Entry<String, List<Army>> e : attacks.entrySet()) {
+				List<Army> list = e.getValue();
+				if (list.size() > 1) {
+					int strongest = 0;
+					int max = Integer.MIN_VALUE;
+					for (int i = 0; i < list.size(); i++) {
+						Army temp = list.get(i);
+						if (temp.strength > max) {
+							max = temp.strength;
+							strongest = i;
+						} else if (temp.strength == max) {
+							list.get(strongest).strength = 0;
+							temp.strength = 0;
+						}
+					}
+				}
+			}
+			// Sort the list
+			Collections.sort(armies);
+			List<String> res = new ArrayList<>();
+			for (Army a : armies) {
+				res.add(a.toString());
+			}
+			return res;
+		}
+	}
+
+	public static class UnitTest {
+		@Test
+		public void test1() {
+			List<String> actions = new ArrayList<>();
+			actions.add("A Paris Hold");
+			actions.add("B Spain Move Paris");
+			actions.add("C London Move Paris");
+			List<String> res = new Solution().play(actions);
+			Assert.assertEquals("A [dead]", res.get(0));
+			Assert.assertEquals("B [dead]", res.get(1));
+			Assert.assertEquals("C [dead]", res.get(2));
+
+			actions.clear();
+			actions.add("A Paris Support B");
+			actions.add("B Spain Move Paris");
+			actions.add("C London Move Paris");
+			List<String> res2 = new Solution().play(actions);
+			Assert.assertEquals("A [dead]", res2.get(0));
+			Assert.assertEquals("B [dead]", res2.get(1));
+			Assert.assertEquals("C [dead]", res2.get(2));
+
+			actions.clear();
+			actions.add("A Brussels Support B");
+			actions.add("B Spain Move Paris");
+			actions.add("C London Move Paris");
+			List<String> res3 = new Solution().play(actions);
+			Assert.assertEquals("A Brussels", res3.get(0));
+			Assert.assertEquals("B Paris", res3.get(1));
+			Assert.assertEquals("C [dead]", res3.get(2));
+
+			actions.clear();
+			actions.add("A Brussels Support B");
+			actions.add("B Spain Move Paris");
+			actions.add("C London Move Paris");
+			actions.add("D Brussels Hold");
+			List<String> res4 = new Solution().play(actions);
+			Assert.assertEquals("A [dead]", res4.get(0));
+			Assert.assertEquals("B [dead]", res4.get(1));
+			Assert.assertEquals("C [dead]", res4.get(2));
+			Assert.assertEquals("D [dead]", res4.get(3));
+
+			actions.clear();
+			actions.add("A Brussels Support B");
+			actions.add("B Spain Move Paris");
+			actions.add("C London Move Paris");
+			actions.add("D London Support C");
+			List<String> res5 = new Solution().play(actions);
+			Assert.assertEquals("A Brussels", res5.get(0));
+			Assert.assertEquals("B [dead]", res5.get(1));
+			Assert.assertEquals("C [dead]", res5.get(2));
+			Assert.assertEquals("D London", res5.get(3));
+		}
+	}
+}