program to find occurence of a number in sorted array using binary search

Author: anishsingh20

Data Structures/LinkedLists/Checking Palindrome List.cpp

@@ -74,9 +74,10 @@ int Palindrome(struct Node *head,stack<int>&s)
 
 	return flag;	
 }
-
 //TIME COMPLEXITY  =  O(n)
 
+
+
 
 
 int main() {
@@ -90,13 +91,13 @@ int main() {
 	struct Node *n4  = new Node();	
 
 
-	n1->data=1;
+	n1->data=2;
 	n1->next=n2;
-	n2->data=2;
+	n2->data=1;
 	n2->next = n3;
-	n3->data=2;
+	n3->data=1;
 	n3->next = n4;
-	n4->data = 1;
+	n4->data = 2;
 	n4->next = NULL;
 
 	struct Node *temp=n1;

Data Structures/LinkedLists/MergePointofLL.cpp

@@ -105,7 +105,8 @@ Node *FindMergePointUsingDiff(Node *headA, Node *headB) {
 	int d = (n-m);
 
 	//if list A is greater in size then simply swap the pointers to head node
-	if(m>n) {
+	if(m>n) 
+	{
 
 	  Node *temp = headA;
 	  headA=headB;
@@ -151,7 +152,7 @@ int main() {
 
 	n1->data = 1;
 	n2->data = 3;
-	n3->data = 100;
+	n3->data = 4;
 	n4->data = 6;
 
 	//creating links

Data Structures/LinkedLists/Singly_LL.cpp

@@ -488,6 +488,28 @@ void CountOccurence(struct Node **head,int data)
 
 }
 
+void SwapList(struct Node *head) {
+	
+	int len = length(head);
+	struct Node  *temp=head;
+	
+	if(head==NULL) {
+		return ;
+	}
+	
+	if(len%2!=0)
+	 {
+	 	cout<<"List not of even length."<<endl;
+	 
+		
+	}
+	else {
+	
+		
+	}
+}
+
+
 //TIME COMPLEXITY = O(n)
 
 
@@ -516,14 +538,14 @@ int main() {
 
 	sortedInsert(&head,10);
 	sortedInsert(&head,9);
-	sortedInsert(&head,10);
+	sortedInsert(&head,1);
 	sortedInsert(&head,20);
-	sortedInsert(&head,2);
-	sortedInsert(&head,51);
-	sortedInsert(&head,6);
-	sortedInsert(&head,61);
-	sortedInsert(&head,10);
-	sortedInsert(&head,60);
+//	sortedInsert(&head,2);
+//	sortedInsert(&head,51);
+//	sortedInsert(&head,6);
+//	sortedInsert(&head,61);
+//	sortedInsert(&head,10);
+//	sortedInsert(&head,60);
 
 
 
@@ -535,9 +557,13 @@ int main() {
 //	
 	cout<<listlength(head)<<endl;
 
-	cout<<"Middle element is :"<<MiddleNode(&head)<<endl;
+	SwapList(head);
+	
+	cout<<listlength(head)<<endl;
+	
+		
+
 
-	CountOccurence(&head,10);
 
 
 

Data Structures/SORTING/QuickSort.cpp

@@ -41,7 +41,7 @@ int Partition(vector<int> &arr,int start, int end) {
 		}	
 	}
 
-	swap(arr[Pindex],arr[end]);//swapping PIVOT and element at Pindex
+	swap(arr[end],arr[Pindex]);//swapping PIVOT and element at Pindex
 
 	return Pindex;//now at the end Pindex is the index of the PIVOT
 }

Data Structures/Searching/OccurenceInArrayUsingBinarySearch.cpp

@@ -0,0 +1,65 @@
+#include<iostream>
+
+//Finding number of occurences of a number in an sorted array using Binary Search
+
+using namespace std;
+
+//Binary search can also be used to find first and last occurences of a repeating number in an array
+
+int BinarySearch(int arr[],int n , int x , bool searchFirst)
+{
+	int l = 0;
+	int h = n-1;
+	int result = -1;
+	while(l <= h)
+	{
+		int mid = (l + (h-l)/2);
+		
+		if(arr[mid]==x) 
+		{
+			result = mid;
+			
+			//if want to search for first occurence or a repeating no
+			if(searchFirst) {
+				//search only in the lower indices
+				 h = mid-1;
+			}
+			//if want to search for the last occurence of a repeating number
+			else {
+				//search only in the higher indices or right subpart of array
+				 l = mid + 1;
+			}
+		}
+		
+		//search in higher indices or right subpart of array
+		else if(arr[mid] <= x)  l = (mid + 1); 
+	
+		//search in lower indices or left subpart of array
+		 else h =  (mid-1);
+		
+	}
+	
+	return result;
+}
+
+
+int main () {
+	
+	int arr [] = {1,2,2,2,3,3,6,7,9};
+	
+	
+	//finding the index of the first occurecne of searched number
+	int firstOcc = BinarySearch(arr,sizeof(arr)/sizeof(arr[0]), 2 , true);
+	
+	if(firstOcc==-1) {
+		
+		cout<<"0 occurence."<<endl;
+	}
+	
+	else {
+		//findind the index of the last occurence of the searched number
+		int lastOcc = BinarySearch(arr,sizeof(arr)/sizeof(arr[0]), 2 , false);
+		
+		cout<<"Count of occurence is :"<<(lastOcc-firstOcc +1)<<endl;
+	}
+}