#Modification 27

Author: amangit1314

arrays/Array_Problem_21.java

@@ -1,4 +1,47 @@
 package arrays;
-/* Problem Title :->  */
+/* 
+ * Problem Title :-> 
+ * Find if there is any sub array with sum equal to 0
+ */
+
+import java.util.*;
+
+/*
+ *  Generalisation
+ *	a[2, 3, -1, -2, 4, 5]; -> The array
+ * 	here their are n^2 + 1 sub arrays, in an array of any size n.
+ * now the sub array of have a sum equal to zero is from index a[1] to index a[3] in this case.
+ */
+
 public class Array_Problem_21 {
+	static Boolean subArrayExists(int[] a) {
+		// Creates an empty hash set h_s
+		Set<Integer> hs = new HashSet<>();
+		// Initialise sum of elements
+		int sum = 0;
+		// Traverse through the given array
+		for(int i = 0; i < a.length; i++) {
+			// Add current element to sum
+			sum += a[i];
+			/*
+			 * Return true in following cases
+			 * a). Current element is 0
+			 * b). sum of elements from 0 to i is 0
+			 * c). sum is already present in hash map
+			 */
+			if(a[i] == 0 || sum == 0 || hs.contains(sum)) return true;
+			// Add sum to hash set
+			hs.add(sum);
+		}
+		// We reach here only when there is no sub_array with 0 sum
+		return false;
+	}
+	// Driver Code
+	public static void main(String[] args) {
+		int[] a = {2, 3, -1, -2, 4, 5};
+		if(subArrayExists(a))
+			System.out.println("Found a subarray with 0 sum");
+		else
+			System.out.println("No Such Sub Array Exists!");
+	}
 }

arrays/Array_Problem_22.java

@@ -1,4 +1,49 @@
 package arrays;
-/* Problem Title :->  */
+/* Problem Title :-> Find factorial of a large number
+ */
 public class Array_Problem_22 {
+	
+	// This function finds factorial of large numbers and prints them
+	static void factorial(int n) {
+		
+		int[] res = new int[500];
+		
+		res[0] = 1;
+		
+		int res_size = 1;
+		
+		for(int x = 2; x <= n; x++)
+			res_size = multiply(x, res, res_size);
+		
+		System.out.println("Factorial of given number is ");
+		
+		for(int i = res_size - 1; i >= 0; i--)
+			System.out.print(res[i]);
+	}
+	
+	// This function multiplies x with the number represented by res[]. 
+	static int multiply(int x, int[] res, int res_size) {
+		
+		int carry = 0;
+		
+		// one by one multiply n with individual digits of res[].
+		for(int i = 0; i < res_size; i++) {
+			int prod = res[i] * x + carry;
+			res[i] = prod % 10;
+			carry = prod/10;
+		}
+		
+		// put carry in res and increase result size
+		while(carry != 0) {
+			res[res_size] = carry % 10;
+			carry = carry/10;
+			res_size++;
+		}
+		return res_size;
+	}
+	
+	// Driver program
+	public static void main(String[] args) {
+		factorial(100);
+	}
 }

arrays/Array_Problem_24.java

@@ -1,4 +1,40 @@
 package arrays;
-/* Problem Title :->  */
+/* 
+ * Problem Title :-> Find longest consecutive subsequence
+ */
+
+import java.util.*;
+
 public class Array_Problem_24 {
+	
+	static int findLogestSubseq(int[] a, int n) {
+		// Sort the array
+		Arrays.sort(a);
+		int ans = 0, count = 0;
+		
+		ArrayList<Integer> v = new ArrayList<>();
+		v.add(10);
+		
+		// Insert repeated elements only once in the vector
+		for(int i = 1; i < n; i++) {
+			if(a[i] != a[i -1]) 	v.add(a[i]);
+		}
+		
+		// Find the max length by traversing the array
+		for(int i = 0; i < v.size(); i++) {
+			// check if the current element is equal to previous element + 1
+			if(i > 0 && v.get(i) == v.get(i - 1) + 1)	count++;
+			else	count = 1;
+			// Update the maximum
+			ans = Math.max(ans, count);
+		}
+		return ans;
+	}
+	
+	// Driver Code
+	public static void main(String[] args) {
+		int[] a = {1,9,3,10,4,20,2};
+		int n = a.length;
+		System.out.println("Length of the Longest "+ "contiguous subsequence is " + findLogestSubseq(a, n));
+	}
 }

arrays/Array_Problem_25.java

@@ -1,4 +1,5 @@
 package arrays;
-/* Problem Title :->  */
+/* Problem Title :-> Given an array of size n and a number k, fin all elements that appear more than " n/k " times.
+ */
 public class Array_Problem_25 {
 }

arrays/Array_Problem_26.java

@@ -1,4 +1,5 @@
 package arrays;
-/* Problem Title :->  */
+/* Problem Title :->  Maximum profit by buying and selling a share atmost twice
+*/
 public class Array_Problem_26 {
 }

arrays/Array_Problem_27.java

@@ -1,6 +1,7 @@
 package arrays;
 
-/* Problem Title :->  */
+/* Problem Title :-> Find whether an array is a subset of another array
+ */
 public class Array_Problem_27 {
 
 

arrays/Array_Problem_28.java

@@ -1,4 +1,5 @@
 package arrays;
-/* Problem Title :->  */
+/* Problem Title :->  Find whether an array is a subset of another array
+*/
 public class Array_Problem_28 {
 }

arrays/Array_Problem_29.java

@@ -1,4 +1,5 @@
 package arrays;
-/* Problem Title :->  */
+/* Problem Title :-> Find the triplet that sum to a given value
+ */
 public class Array_Problem_29 {
 }

arrays/Array_Problem_4_Approach1.java

@@ -1,3 +1,4 @@
+
 package arrays;
 import java.io.*;
 

binary_search_tree/Deletion_of_a_node_in_bst.java

@@ -1,3 +1,5 @@
+package binary_search_tree;
+
 /**
  * Deletion_of_a_node_in_bst
  */