2 files changed, 131 insertions, 0 deletions
diff --git a/AlgoDesignAndTechniqueEdxJava/sources/LargestNumber.java b/AlgoDesignAndTechniqueEdxJava/sources/LargestNumber.java
new file mode 100644
index 0000000..0458b91
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/sources/LargestNumber.java
@@ -0,0 +1,59 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Scanner;
+
+public class LargestNumber {
+
+	public static void main(String[] args) {
+		Scanner scanner = new Scanner(System.in);
+		int n = scanner.nextInt();
+		String[] a = new String[n];
+		for (int i = 0; i < n; i++) {
+			a[i] = scanner.next();
+		}
+		System.out.println(getLargestNumber(a));
+	}
+
+	public static String getLargestNumber(String[] numbers) {
+		List<String> numList = new ArrayList<String>(Arrays.asList(numbers));
+		String result = "";
+		String maxDigit = "0";
+		int indexHolder = 0;
+		while (numList.size() > 0) {
+			for (int i = 0; i < numList.size(); i++) {
+				if (compareLeadingDigit(numList.get(i), maxDigit)) {
+					maxDigit = numList.get(i);
+					indexHolder = i;
+				}
+			}
+			result = result + maxDigit;
+			maxDigit = "0";
+			numList.remove(indexHolder);
+		}
+		return result;
+	}
+
+	public static boolean compareLeadingDigit(String string, String maxDigit) {
+		if (string.length() == maxDigit.length())
+			return Integer.parseInt(string) > Integer.parseInt(maxDigit);
+		if (string.length() < maxDigit.length()) {
+			if (string.charAt(0) > maxDigit.charAt(0)) {
+				return true;
+			} else if (string.charAt(0) < maxDigit.charAt(0)) {
+				return false;
+			} else if (string.charAt(0) > maxDigit.charAt(1)) {
+				return true;
+			} else if (string.charAt(0) < maxDigit.charAt(1)) {
+				return false;
+			} else if (maxDigit.length() == 2)
+				return false;
+			else {
+				return string.charAt(0) > maxDigit.charAt(2);
+			}
+		} else {
+			return !compareLeadingDigit(maxDigit, string);
+		}
+	}
+
+}
diff --git a/AlgoDesignAndTechniqueEdxJava/tests/LargestNumberTest.java b/AlgoDesignAndTechniqueEdxJava/tests/LargestNumberTest.java
new file mode 100644
index 0000000..285d502
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/tests/LargestNumberTest.java
@@ -0,0 +1,72 @@
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class LargestNumberTest {
+
+	@Test
+	void test1() {
+		String[] numbers = {"9", "4", "6", "1", "9"};
+		assertEquals("99641", LargestNumber.getLargestNumber(numbers));
+	}
+
+	@Test
+	void test2() {
+		String[] numbers = {"21", "2"};
+		assertEquals("221", LargestNumber.getLargestNumber(numbers));
+	}
+
+	@Test
+	void test3() {
+		String[] numbers = {"23", "39", "92"};
+		assertEquals("923923", LargestNumber.getLargestNumber(numbers));
+	}
+
+	@Test
+	void test4() {
+		String[] numbers = {"23", "39", "92"};
+		assertEquals("923923", LargestNumber.getLargestNumber(numbers));
+	}
+
+	@Test
+	void test5() {
+		String[] numbers = {"23", "2"};
+		assertEquals("232", LargestNumber.getLargestNumber(numbers));
+	}
+
+	@Test
+	void testCompareLeadingDigit() {
+		assertTrue(LargestNumber.compareLeadingDigit("2", "21"));
+	}
+
+	@Test
+	void testCompareLeadingDigit1() {
+		assertFalse(LargestNumber.compareLeadingDigit("20", "21"));
+	}
+
+	@Test
+	void testCompareLeadingDigit2() {
+		assertFalse(LargestNumber.compareLeadingDigit("321", "322"));
+	}
+
+	@Test
+	void testCompareLeadingDigit3() {
+		assertFalse(LargestNumber.compareLeadingDigit("321", "32"));
+	}
+
+	@Test
+	void testCompareLeadingDigit4() {
+		assertFalse(LargestNumber.compareLeadingDigit("10", "1"));
+	}
+
+	@Test
+	void testCompareLeadingDigit5() {
+		assertTrue(LargestNumber.compareLeadingDigit("6", "10"));
+	}
+
+	@Test
+	void testCompareLeadingDigit6() {
+		assertTrue(LargestNumber.compareLeadingDigit("23", "2"));
+	}
+	
+}