diff --git a/Exercise_1.java b/Exercise_1.java
index c3ff1141..690f2751 100644
--- a/Exercise_1.java
+++ b/Exercise_1.java
@@ -1,21 +1,42 @@
-class BinarySearch { 
-    // Returns index of x if it is present in arr[l.. r], else return -1 
-    int binarySearch(int arr[], int l, int r, int x) 
-    { 
-        //Write your code here
-    } 
-  
-    // Driver method to test above 
-    public static void main(String args[]) 
-    { 
-        BinarySearch ob = new BinarySearch(); 
-        int arr[] = { 2, 3, 4, 10, 40 }; 
-        int n = arr.length; 
-        int x = 10; 
-        int result = ob.binarySearch(arr, 0, n - 1, x); 
-        if (result == -1) 
-            System.out.println("Element not present"); 
+// Time Complexity : O(log n)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+class BinarySearch {
+    // Returns index of x if it is present in arr[l.. r], else return -1
+    // In binary search we divide the array into half repeatedly to search for the
+    // target value
+    // Works for sorted list only
+    int binarySearch(int arr[], int l, int r, int x) {
+        // Write your code here
+        while (l <= r) {
+            int midPosition = (l + r) / 2;
+            int mid = arr[midPosition];
+            if (x == mid) {
+                // If target value is equal to the mid value return index of mid value
+                return midPosition;
+            } else if (x < mid) {
+                // If target value is less than the mid value, search in the left sub array
+                r = midPosition - 1;
+            } else if (x > mid) {
+                // If target value is greater than the mid value, search in the right sub array
+                l = midPosition + 1;
+            }
+        }
+        return -1;
+    }
+
+    // Driver method to test above
+    public static void main(String args[]) {
+        BinarySearch ob = new BinarySearch();
+        int arr[] = { 2, 3, 4, 10, 40 };
+        int n = arr.length;
+        int x = 10;
+        int result = ob.binarySearch(arr, 0, n - 1, x);
+        if (result == -1)
+            System.out.println("Element not present");
         else
-            System.out.println("Element found at index " + result); 
-    } 
-} 
+            System.out.println("Element found at index " + result);
+    }
+}
diff --git a/Exercise_2.java b/Exercise_2.java
index d0b5fa5f..db77412e 100644
--- a/Exercise_2.java
+++ b/Exercise_2.java
@@ -1,48 +1,83 @@
-class QuickSort 
-{ 
-    /* This function takes last element as pivot, 
-       places the pivot element at its correct 
-       position in sorted array, and places all 
-       smaller (smaller than pivot) to left of 
-       pivot and all greater elements to right 
-       of pivot */
-    void swap(int arr[],int i,int j){
-        //Your code here   
+// Time Complexity : Not sure
+// Space Complexity : Not sure
+// Did this code successfully run on Leetcode : 
+// Any problem you faced while coding this : Referred some documention and videos and coded. Not getting what will be time complexity
+
+class QuickSort {
+    /*
+     * This function takes last element as pivot,
+     * places the pivot element at its correct
+     * position in sorted array, and places all
+     * smaller (smaller than pivot) to left of
+     * pivot and all greater elements to right
+     * of pivot
+     */
+    void swap(int arr[], int i, int j) {
+        // Your code here
+        int temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
     }
-    
-    int partition(int arr[], int low, int high) 
-    { 
-   	//Write code here for Partition and Swap 
-    } 
-    /* The main function that implements QuickSort() 
-      arr[] --> Array to be sorted, 
-      low  --> Starting index, 
-      high  --> Ending index */
-    void sort(int arr[], int low, int high) 
-    {  
-            // Recursively sort elements before 
-            // partition and after partition 
-    } 
-  
+
+    int partition(int arr[], int low, int high) {
+
+        // Write code here for Partition and Swap
+        // Taking the last element as pivot
+        int pivot = arr[high];
+        // Pointer for swap position
+        int i = low - 1;
+        // Another pointer j that will start from first element, comparing each element
+        // with pivot
+        for (int j = low; j < high; j++) {
+            // If any element less than pivot, swap it the element at index i
+            if (arr[j] <= pivot) {
+                i++;
+                swap(arr, i, j);
+            }
+        }
+        // Swap pivot and place it in correct position
+        swap(arr, i + 1, high);
+        return i + 1;
+    }
+
+    /*
+     * The main function that implements QuickSort()
+     * arr[] --> Array to be sorted,
+     * low --> Starting index,
+     * high --> Ending index
+     */
+    void sort(int arr[], int low, int high) {
+        // Recursively sort elements before
+        // partition and after partition
+
+        if (low < high) {
+            int pi = partition(arr, low, high);
+            // System.out.println(pi);
+            // Recursively call sort
+            sort(arr, low, pi - 1);
+            sort(arr, pi + 1, high);
+
+        }
+
+    }
+
     /* A utility function to print array of size n */
-    static void printArray(int arr[]) 
-    { 
-        int n = arr.length; 
-        for (int i=0; i<n; ++i) 
-            System.out.print(arr[i]+" "); 
-        System.out.println(); 
-    } 
-  
-    // Driver program 
-    public static void main(String args[]) 
-    { 
-        int arr[] = {10, 7, 8, 9, 1, 5}; 
-        int n = arr.length; 
-  
-        QuickSort ob = new QuickSort(); 
-        ob.sort(arr, 0, n-1); 
-  
-        System.out.println("sorted array"); 
-        printArray(arr); 
-    } 
-} 
+    static void printArray(int arr[]) {
+        int n = arr.length;
+        for (int i = 0; i < n; ++i)
+            System.out.print(arr[i] + " ");
+        System.out.println();
+    }
+
+    // Driver program
+    public static void main(String args[]) {
+        int arr[] = { 10, 7, 8, 9, 1, 5 };
+        int n = arr.length;
+
+        QuickSort ob = new QuickSort();
+        ob.sort(arr, 0, n - 1);
+
+        System.out.println("sorted array");
+        printArray(arr);
+    }
+}
diff --git a/Exercise_3.java b/Exercise_3.java
index 1f9b752a..382ff8bb 100644
--- a/Exercise_3.java
+++ b/Exercise_3.java
@@ -1,53 +1,62 @@
-class LinkedList 
-{ 
-    Node head; // head of linked list 
-  
+// Time Complexity : O(n)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : Referred some documention and videos and coded
+
+class LinkedList {
+    Node head; // head of linked list
+
     /* Linked list node */
-    class Node 
-    { 
-        int data; 
-        Node next; 
-        Node(int d) 
-        { 
-            data = d; 
-            next = null; 
-        } 
-    } 
-  
+    class Node {
+        int data;
+        Node next;
+
+        Node(int d) {
+            data = d;
+            next = null;
+        }
+    }
+
     /* Function to print middle of linked list */
-   //Complete this function
-    void printMiddle() 
-    { 
-        //Write your code here
-	//Implement using Fast and slow pointers
-    } 
-  
-    public void push(int new_data) 
-    { 
-        Node new_node = new Node(new_data); 
-        new_node.next = head; 
-        head = new_node; 
-    } 
-
-    public void printList() 
-    { 
-        Node tnode = head; 
-        while (tnode != null) 
-        { 
-            System.out.print(tnode.data+"->"); 
-            tnode = tnode.next; 
-        } 
-        System.out.println("NULL"); 
-    } 
-  
-    public static void main(String [] args) 
-    { 
-        LinkedList llist = new LinkedList(); 
-        for (int i=15; i>0; --i) 
-        { 
-            llist.push(i); 
-            llist.printList(); 
-            llist.printMiddle(); 
-        } 
-    } 
-} 
\ No newline at end of file
+    // Complete this function
+    void printMiddle() {
+        // Start both slow and fast pointer from head
+        Node slp = head;
+        Node fp = head;
+
+        while (fp != null && fp.next != null) {
+            // Increment fast pointer by 2 till last element
+            fp = fp.next.next;
+            // Increment slow pointer by 1
+            slp = slp.next;
+
+        }
+        // As soon as the fast pointer reaches the end, the slow pointer will reach at
+        // the mid position
+        System.out.println("Middle " + slp.data);
+    }
+
+    public void push(int new_data) {
+        Node new_node = new Node(new_data);
+        new_node.next = head;
+        head = new_node;
+    }
+
+    public void printList() {
+        Node tnode = head;
+        while (tnode != null) {
+            System.out.print(tnode.data + "->");
+            tnode = tnode.next;
+        }
+        System.out.println("NULL");
+    }
+
+    public static void main(String[] args) {
+        LinkedList llist = new LinkedList();
+        for (int i = 15; i > 0; --i) {
+            llist.push(i);
+            llist.printList();
+            llist.printMiddle();
+        }
+    }
+}
\ No newline at end of file
diff --git a/Exercise_4.java b/Exercise_4.java
index 81afd3c2..9ba87eb4 100644
--- a/Exercise_4.java
+++ b/Exercise_4.java
@@ -1,42 +1,97 @@
-class MergeSort 
-{ 
-    // Merges two subarrays of arr[]. 
-    // First subarray is arr[l..m] 
-    // Second subarray is arr[m+1..r] 
-    void merge(int arr[], int l, int m, int r) 
-    {  
-       //Your code here  
-    } 
-  
-    // Main function that sorts arr[l..r] using 
-    // merge() 
-    void sort(int arr[], int l, int r) 
-    { 
-	//Write your code here
-        //Call mergeSort from here 
-    } 
-  
+// Time Complexity : Not sure
+// Space Complexity : Not sure
+// Did this code successfully run on Leetcode : 
+// Any problem you faced while coding this : Referred some documention and videos and coded but did not understood properly
+
+class MergeSort {
+    // Merges two subarrays of arr[].
+    // First subarray is arr[l..m]
+    // Second subarray is arr[m+1..r]
+    void merge(int arr[], int l, int m, int r) {
+        // Your code here
+        // length of two arrays to merge
+        int n1 = m - l + 1;
+        int n2 = r - m;
+
+        // Declare 2 arrays
+        int[] L = new int[n1];
+        int[] R = new int[n2];
+
+        // For each of the two arrays, add values
+        for (int i = 0; i < n1; i++) {
+            L[i] = arr[l + i];
+
+        }
+        for (int j = 0; j < n2; j++) {
+            R[j] = arr[m + 1 + j];
+
+        }
+        int i = 0, j = 0;
+        int k = l;
+
+        // Then compare two arrays and insert in original one to get the final sorted
+        // array
+        while (i < n1 && j < n2) {
+            if (L[i] < R[j]) {
+                arr[k] = L[i];
+                i++;
+            } else {
+                arr[k] = R[j];
+                j++;
+            }
+            k++;
+
+        }
+
+        // For remaining elements in any of the one array, simply add all
+        while (i < n1) {
+            arr[k] = L[i];
+            i++;
+            k++;
+        }
+        while (j < n2) {
+            arr[k] = R[j];
+            j++;
+            k++;
+        }
+
+    }
+
+    // Main function that sorts arr[l..r] using
+    // merge()
+    void sort(int arr[], int l, int r) {
+        // Write your code here
+        // Call mergeSort from here
+
+        if (l < r) {
+            int m = (l + (r)) / 2;
+            // Divide till it is single element
+            sort(arr, l, m);
+            sort(arr, m + 1, r);
+            // Merge the sorted arrays
+            merge(arr, l, m, r);
+        }
+    }
+
     /* A utility function to print array of size n */
-    static void printArray(int arr[]) 
-    { 
-        int n = arr.length; 
-        for (int i=0; i<n; ++i) 
-            System.out.print(arr[i] + " "); 
-        System.out.println(); 
-    } 
-  
-    // Driver method 
-    public static void main(String args[]) 
-    { 
-        int arr[] = {12, 11, 13, 5, 6, 7}; 
-  
-        System.out.println("Given Array"); 
-        printArray(arr); 
-  
-        MergeSort ob = new MergeSort(); 
-        ob.sort(arr, 0, arr.length-1); 
-  
-        System.out.println("\nSorted array"); 
-        printArray(arr); 
-    } 
-} 
\ No newline at end of file
+    static void printArray(int arr[]) {
+        int n = arr.length;
+        for (int i = 0; i < n; ++i)
+            System.out.print(arr[i] + " ");
+        System.out.println();
+    }
+
+    // Driver method
+    public static void main(String args[]) {
+        int arr[] = { 12, 11, 13, 5, 6, 7 };
+
+        System.out.println("Given Array");
+        printArray(arr);
+
+        MergeSort ob = new MergeSort();
+        ob.sort(arr, 0, arr.length - 1);
+
+        System.out.println("\nSorted array");
+        printArray(arr);
+    }
+}
\ No newline at end of file
diff --git a/Exercise_5.java b/Exercise_5.java
index 30e82675..c48914c1 100644
--- a/Exercise_5.java
+++ b/Exercise_5.java
@@ -1,36 +1,80 @@
-class IterativeQuickSort { 
-    void swap(int arr[], int i, int j) 
-    { 
-	//Try swapping without extra variable 
-    } 
-  
-    /* This function is same in both iterative and 
-       recursive*/
-    int partition(int arr[], int l, int h) 
-    { 
-        //Compare elements and swap.
-    } 
-  
-    // Sorts arr[l..h] using iterative QuickSort 
-    void QuickSort(int arr[], int l, int h) 
-    { 
-        //Try using Stack Data Structure to remove recursion.
-    } 
-  
-    // A utility function to print contents of arr 
-    void printArr(int arr[], int n) 
-    { 
-        int i; 
-        for (i = 0; i < n; ++i) 
-            System.out.print(arr[i] + " "); 
-    } 
-  
-    // Driver code to test above 
-    public static void main(String args[]) 
-    { 
-        IterativeQuickSort ob = new IterativeQuickSort(); 
-        int arr[] = { 4, 3, 5, 2, 1, 3, 2, 3 }; 
-        ob.QuickSort(arr, 0, arr.length - 1); 
-        ob.printArr(arr, arr.length); 
-    } 
-} 
\ No newline at end of file
+// Time Complexity : Not sure
+// Space Complexity : Not sure
+// Did this code successfully run on Leetcode : 
+// Any problem you faced while coding this : Referred some documention and videos and coded but did not understood properly and not sure how this time complexity?
+
+import java.util.Stack;
+
+class IterativeQuickSort {
+    void swap(int arr[], int i, int j) {
+        // Try swapping without extra variable
+        if (i != j) {
+            arr[i] = arr[i] + arr[j];
+            arr[j] = arr[i] - arr[j];
+            arr[i] = arr[i] - arr[j];
+        }
+    }
+
+    /*
+     * This function is same in both iterative and
+     * recursive
+     */
+    int partition(int arr[], int l, int h) {
+        // Compare elements and swap.
+        int pivot = arr[h];
+        int i = l - 1;
+
+        for (int j = l; j < h; j++) {
+            if (arr[j] <= pivot) {
+                i++;
+                swap(arr, i, j);
+            }
+
+        }
+
+        swap(arr, i + 1, h);
+        return i + 1;
+    }
+
+    // Sorts arr[l..h] using iterative QuickSort
+    void QuickSort(int arr[], int l, int h) {
+        // Declare stack
+        Stack<Integer> stack = new Stack<>();
+        // Push the low and high values
+        stack.push(l);
+        stack.push(h);
+
+        while (!stack.isEmpty()) {
+            // Pop from the stack and get the partion index and iteratively repeat it on the
+            // sub arrays
+            int high = stack.pop();
+            int low = stack.pop();
+            if (low < high) {
+                int pi = partition(arr, low, high);
+
+                stack.push(low);
+                stack.push(pi - 1);
+
+                stack.push(pi + 1);
+                stack.push(high);
+            }
+
+        }
+
+    }
+
+    // A utility function to print contents of arr
+    void printArr(int arr[], int n) {
+        int i;
+        for (i = 0; i < n; ++i)
+            System.out.print(arr[i] + " ");
+    }
+
+    // Driver code to test above
+    public static void main(String args[]) {
+        IterativeQuickSort ob = new IterativeQuickSort();
+        int arr[] = { 4, 3, 5, 2, 1, 3, 2, 3 };
+        ob.QuickSort(arr, 0, arr.length - 1);
+        ob.printArr(arr, arr.length);
+    }
+}
\ No newline at end of file