Day 4 problem solution

src/main/java/org/jugbd/marathon/day2/BiggestNumber.java

@@ -1,50 +1,34 @@
 package org.jugbd.marathon.day2;
 
-import java.util.Arrays;
-
 public class BiggestNumber {
-    public static long findTheNextBiggerNumber(long n) {
-
-        int ar[] = new int[20]; // long is 64 bit, so max 19 digits can be possible
-        int length = 0, tmp;
-        boolean found = false;
-        while (n > 0) {
-
-            ar[length++] = (int) (n % 10);
-            n /= 10;
-        }
-
-        for (int i = 0, j = length - 1; i < length / 2; i++, j--) {
-            tmp = ar[i];
-            ar[i] = ar[j];
-            ar[j] = tmp;
-        }
-
-        // 52876
-
-        for (int i = length - 1; i >= 0; i--) {
-            for (int j = i - 1; j >= 0; j--) {
-                if (ar[j] < ar[i]) {
-
-                    tmp = ar[i];
-                    ar[i] = ar[j];
-                    ar[j] = tmp;
-                    Arrays.sort(ar, j + 1, length);
-                    found = true;
-                    break;
-                }
-            }
-
-            if (found) {
-                break;
-            }
-        }
-
-        n = 0;
-        for (int i = 0; i < length; i++) {
-            n = n * 10 + ar[i];
-        }
-
-        return found ? n : -1;
-    }
+	public static long findTheNextBiggerNumber(long n) {
+
+		char[] digits = String.valueOf(n).toCharArray();
+		if (digits.length == 1)
+			return -1;
+		for (int i = digits.length - 2; i >= 0; i--) {
+			int index = getImmediateMaxDigitAsIndex(digits, i + 1, digits.length, digits[i]);
+			if (index != -1) {
+				char ch = digits[index];
+				for (int j = index - 1; j >= i; j--) {
+					digits[j + 1] = digits[j];
+				}
+				digits[i] = ch;
+				return Long.parseLong(new String(digits));
+			}
+		}
+		return -1;
+	}
+
+	static int getImmediateMaxDigitAsIndex(char[] digits, int startInd, int endInd, char givenDigit) {
+		int index = -1;
+		char min = '9';
+		for (int i = startInd; i < endInd; i++) {
+			if (digits[i] > givenDigit && min > digits[i]) {
+				index = i;
+				min = digits[i];
+			}
+		}
+		return index;
+	}
 }

src/main/java/org/jugbd/marathon/day3/TrappingTheRainWater.java

@@ -1,35 +1,31 @@
 package org.jugbd.marathon.day3;
 
-
 public class TrappingTheRainWater {
-    static int findWaterUnit(int[] arr) {
-
-    	int unitOfWater = 0, i, j, k;
-		 boolean checked[] = new boolean[arr.length];
-
-		 for(i=0;i<arr.length;i++) {
-
-			 checked[i] = false;
-		 }
-
-		 for(i=0;i<arr.length;i++) {
-
-			 if(checked[i] == false) { 
-
-				 for(j=i+1;j<arr.length;j++) {
-
-					 if(arr[i] <= arr[j] && checked[j] == false) {
-
-						 for(k=i+1;k<j;k++) {
-
-							 unitOfWater += (arr[i]-arr[k]);
-							 checked[k] = true;
-						 }
-						 break;
-					 }
-				 }
-			 } 
-		 }
-		 return unitOfWater;
-    }
+	static int findWaterUnit(int[] arr) {
+		int unitOfWater = 0;
+		int length = arr.length - 1;
+		int i = 0;
+		while (i < length) {
+			if (arr[i] != 0) {
+				int j = i + 1;
+				int sum = 0;
+				boolean canHold = true;
+				while (arr[i] > arr[j]) {
+					sum += arr[i] - arr[j];
+					if (j == length) {
+						canHold = false;
+						break;
+					}
+					j++;
+				}
+				if (canHold) {
+					unitOfWater += sum;
+					i = j;
+					continue;
+				}
+			}
+			i++;
+		}
+		return unitOfWater;
+	}
 }

src/main/java/org/jugbd/marathon/day4/Directory.java

@@ -1,29 +1,48 @@
 package org.jugbd.marathon.day4;
 
+import java.util.ArrayList;
 import java.util.Date;
-
-public class Directory {
-    private String name;
-    private Date createdDate;
-
-    public Directory(String root) {
-
-    }
-
-    public void add(File file) {
-
-    }
-
-    public int numberOfFiles() {
-
-        return 0;
-    }
-
-    public Object getName() {
-        return name;
-    }
-
-    public Date getCreatedDate() {
-        return createdDate;
-    }
+import java.util.List;
+
+public class Directory extends FileSystemComponent {
+	private String name;
+	private Date createdDate;
+	private List<FileSystemComponent> files = new ArrayList<>();
+
+	public Directory(String root) {
+		if (root == null || root.isEmpty()) {
+			throw new IllegalArgumentException(
+					"Directory name shouldn't be null or empty string");
+		}
+		this.name = root;
+		this.createdDate = new Date();
+	}
+
+	@Override
+	public void add(FileSystemComponent fileComponent) {
+		if (files.contains(fileComponent)) {
+			throw new IllegalArgumentException(fileComponent.getName()
+					+ " already exists in " + this.getName() + " directory");
+		} else if (fileComponent.hashCode() == this.hashCode()
+				&& fileComponent.getName().equals(this.getName())) {
+			throw new IllegalArgumentException(
+					"A parent directory can't hold itself as its child component");
+		}
+		files.add(fileComponent);
+	}
+
+	@Override
+	public int numberOfFiles() {
+		return files.size();
+	}
+
+	@Override
+	public String getName() {
+		return name;
+	}
+
+	@Override
+	public Date getCreatedDate() {
+		return createdDate;
+	}
 }

src/main/java/org/jugbd/marathon/day4/File.java

@@ -1,14 +1,18 @@
 package org.jugbd.marathon.day4;
 
+public class File extends FileSystemComponent{
+	private String name;
 
-public class File {
-    private String name;
-
-    public File(String name) {
-
-    }
-
-    public String getName() {
-        return name;
-    }
+	public File(String name) {
+		if (name == null || name.isEmpty()) {
+			throw new IllegalArgumentException(
+					"Directory name shouldn't be null or empty string");
+		}
+		this.name = name;
+	}
+
+	@Override
+	public String getName() {
+		return name;
+	}
 }

src/main/java/org/jugbd/marathon/day4/FileSystemComponent.java

@@ -0,0 +1,22 @@
+package org.jugbd.marathon.day4;
+
+import java.util.Date;
+
+public abstract class FileSystemComponent {
+
+	public String getName() {
+		throw new UnsupportedOperationException();
+	}
+
+	public int numberOfFiles() {
+		throw new UnsupportedOperationException();
+	}
+
+	public void add(FileSystemComponent fileSystemComponent) {
+		throw new UnsupportedOperationException();
+	}
+
+	public Date getCreatedDate() {
+		throw new UnsupportedOperationException();
+	}
+}

src/test/java/org/jugbd/marathon/day2/BiggestNumberTest.java

@@ -17,5 +17,7 @@ public void basicTests() {
         assertEquals(-1, BiggestNumber.findTheNextBiggerNumber(111));
         assertEquals(-1, BiggestNumber.findTheNextBiggerNumber(531));
         assertEquals(753772, BiggestNumber.findTheNextBiggerNumber(737752));
+        assertEquals(5499214, BiggestNumber.findTheNextBiggerNumber(5499142));
+        assertEquals(219, BiggestNumber.findTheNextBiggerNumber(192));
     }
 }

src/test/java/org/jugbd/marathon/day3/TrappingTheRainWaterTest.java

@@ -12,5 +12,7 @@ public void basicTest() {
         assertEquals(2, TrappingTheRainWater.findWaterUnit(new int[]{2, 0, 2}));
         assertEquals(10, TrappingTheRainWater.findWaterUnit(new int[]{3, 0, 0, 2, 0, 4}));
         assertEquals(6, TrappingTheRainWater.findWaterUnit(new int[]{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}));
+        assertEquals(0, TrappingTheRainWater.findWaterUnit(new int[]{0, 1, 0}));
+        assertEquals(4, TrappingTheRainWater.findWaterUnit(new int[]{3, 4, 0, 5, 2, 3, 0, 0}));
     }
 }

src/test/java/org/jugbd/marathon/day4/FileSystemTest.java

@@ -1,35 +1,62 @@
 package org.jugbd.marathon.day4;
 
-
-import org.junit.Test;
-
-import java.util.Date;
-
 import static junit.framework.TestCase.assertEquals;
 import static junit.framework.TestCase.assertNotNull;
 
-public class FileSystemTest {
-
-
-    @Test
-    public void basicTest() {
-        String rootDirectoryName = "root";
-        Directory root = new Directory(rootDirectoryName);
-        assertNotNull(root);
-        assertEquals(rootDirectoryName, root.getName());
-
-        String fileName = "profile.jpg";
-        File file = new File(fileName);
-        assertNotNull(file);
-
-        assertEquals(fileName, file.getName());
+import java.util.Date;
 
-        root.add(file);
-        assertEquals(1, root.numberOfFiles());
+import org.junit.Test;
 
-        Date createdDate = root.getCreatedDate();
-        assertNotNull(createdDate);
+public class FileSystemTest {
 
-        //Add more test cases
-    }
+	@Test
+	public void basicTest() {
+		String rootDirectoryName = "root";
+		Directory root = new Directory(rootDirectoryName);
+		assertNotNull(root);
+		assertEquals(rootDirectoryName, root.getName());
+
+		String fileName = "profile.jpg";
+		File file = new File(fileName);
+		assertNotNull(file);
+
+		assertEquals(fileName, file.getName());
+
+		root.add(file);
+		assertEquals(1, root.numberOfFiles());
+
+		Date createdDate = root.getCreatedDate();
+		assertNotNull(createdDate);
+
+		FileSystemComponent dir2 = new Directory("Dir2");
+		root.add(dir2);
+		assertEquals(2, root.numberOfFiles());
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testDuplicateFileExistance() {
+		FileSystemComponent root = new Directory("root");
+		File file = new File("profile.jpg");
+		root.add(file);
+		root.add(file);
+		assertEquals(1, root.numberOfFiles());
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testEmptyOrNullDirectoryName(){
+		new Directory(null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testEmptyOrNullFileName(){
+		new File("");
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testParentAsAChild(){
+		FileSystemComponent root = new Directory("root");
+		root.add(root);
+	}
+
+
 }