MajorElement.java

Java/FirstAndLastOccur.java

@@ -0,0 +1,75 @@
+/******************************************************************************
+Given an array of integers nums sorted in ascending order, find the starting and 
+ending position of a given target value using "Modified Binary Search"
+Leetcode Link- https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
+*******************************************************************************/
+import java.util.Scanner;
+public class FirstAndLastOccur
+{
+
+    //finding first Occurrence
+    public static int firstOccur(int n, int[] arr, int find) {
+        int l=0, r=n-1;
+        int start=-1;
+		if(arr[0]==find) {
+		    start=0;
+		}else {
+		    while(l<=r) {
+    		    int mid=l+(r-l)/2;
+    		    if(mid>0 && arr[mid]==find && arr[mid-1]!=find) {
+    		        start=mid;
+    		        break;
+    		    } else if(arr[mid]>=find) {
+                    r--;
+    		    } else {
+    		        l++;
+    		    }
+		    }   
+		}  
+		return start; 
+    }
+
+    //finding last Occurrence
+    public static int lastOccur(int n, int[] arr, int find) {
+        int l=0, r=n-1;
+        int end=-1;
+		if(arr[n-1]==find) {
+		    end=n-1;
+		}else {
+		    while(l<=r) {
+    		    int mid=l+(r-l)/2;
+    		    if(mid<n-1 && arr[mid]==find && arr[mid+1]!=find) {
+    		        end=mid;
+    		        break;
+    		    } else if(arr[mid]<=find) {
+                    l++;
+    		    } else {
+    		        r--;
+    		    }
+		    }   
+		}  
+		return end; 
+    }
+	public static void main(String[] args) {
+		Scanner sc=new Scanner(System.in);
+		int n=sc.nextInt();
+		int[] arr=new int[n];
+		for(int i=0; i<n; i++)
+		    arr[i]=sc.nextInt();
+		int find=sc.nextInt();
+		int start=firstOccur(n, arr, find); //takes O(log n) time
+		int end=lastOccur(n, arr, find); //takes O(log n) time
+		if (start==-1 || end==-1) {
+		    System.out.println("Element not found");
+		} else {
+		    System.out.println("First Occurrence: "+(start+1)+"  Last Occurrence: "+(end+1));
+		}
+	}
+}
+
+//Input: 5
+//       2 2 2 3 4
+//       2
+//Output: First Occurrence: 1   Last Occurrence: 3
+
+//Time Complexity: O(log n)

Java/MajorElement.java

@@ -0,0 +1,55 @@
+/******************************************************************************
+Major Element-> element having more than n/2 occurrence in an array
+
+Mostly asked in Big tech Comapnies Interviews
+Leetcode Link-> https://leetcode.com/problems/majority-element/
+*******************************************************************************/
+import java.util.Scanner;
+
+public class MajorElement
+{
+	public static void main(String[] args) {
+		Scanner sc=new Scanner(System.in);
+		int n=sc.nextInt();
+		int[] arr=new int[n];
+		for(int i=0; i<n; i++) {
+		    arr[i]=sc.nextInt();
+		}
+		int maxElement=arr[0];   //initially let major element
+		int counter=1;
+
+		//check for possible major element
+		for(int i=1; i<n; i++) {
+            if(arr[i]==maxElement) {
+                counter++;
+            } else if(counter>0) {
+                counter--;
+            } else {
+                counter=1;
+                maxElement=arr[i];
+            } 
+		}
+		int maxOccur=0;
+		if(counter>0) {
+		    for(int element:arr) {
+		        if(element==maxElement) 
+		            maxOccur++;
+		    }
+		}
+		if(maxOccur>n/2) {
+		    System.out.println("Major Element is: "+maxElement);
+		}else {
+		    System.out.println(" No Major Element is");
+		}
+	}
+}
+
+//Input-1: 6
+//         2 2 2 4 5 2 
+//Output-1: Major Element is: 2
+
+//Input-2: 9
+//         4 4 4 4 5 2 4 4 5 
+//Output-2: Major Element is: 4
+
+//Time Complexity-O(n)