diff --git a/DS/C/Lab/Week11/expression.c b/DS/C/Lab/Week11/expression.c
new file mode 100644
index 0000000..499b333
--- /dev/null
+++ b/DS/C/Lab/Week11/expression.c
@@ -0,0 +1,125 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include<stdbool.h>
+#include<ctype.h>
+#include<string.h>
+#define MAX 100
+
+typedef struct TNode *Tptr;
+typedef struct TNode
+{
+    char data;
+    Tptr leftchild;
+    Tptr rightchild;
+}TNode;
+///*
+//Create nodes in the tree
+Tptr createNode(char val)
+{
+    Tptr temp =(Tptr)malloc(sizeof(TNode));
+    temp->data = val;
+    temp->leftchild = temp->rightchild = NULL;
+    return temp;
+}
+//*/
+
+Tptr stack[MAX];
+int top=-1;
+int i;
+
+//check if stack is empty
+bool isEmpty()
+{
+    return top==-1;
+}
+
+//check if stack is full
+bool isFull()
+{
+    return top==MAX -1;
+}
+
+//push element onto stack
+void Push(Tptr e)
+{
+    if(isFull())
+    {
+        return;
+    }
+    stack[++top]=e;
+}
+
+//pop element from stack
+Tptr Pop()
+{
+    Tptr popped=createNode('\0');
+    if(isEmpty())
+    {
+        free(popped);
+    }
+    else
+    {
+        popped=stack[top--];
+    }
+    return popped;
+}
+
+//check if character is operator
+bool isOperator(char ch)
+{
+    bool ret=false;
+    if(ch=='*' || ch=='/' || ch=='+' || ch=='-' || ch=='^' )
+    {
+        ret = true;
+    }
+    return ret;
+}
+
+Tptr createExpression(char* postfix)
+{
+    int i;
+    int plen =strlen(postfix);
+    char cc;
+    for(i=0;i<plen;i++)
+    {
+        cc = postfix[i];
+        if(isalnum(cc))
+        {
+            Tptr node = createNode(cc);
+            Push(node);
+        }
+        else if(isOperator(cc))
+        {
+            Tptr node = createNode(cc);
+            node->rightchild = Pop();
+            node->leftchild = Pop();
+            Push(node);
+        }
+    }
+    return stack[top];
+}
+
+void inOrderTraversal(Tptr root)
+{
+    if (root != NULL)
+    {
+        inOrderTraversal(root->leftchild);
+        printf("%c ", root->data);
+        inOrderTraversal(root->rightchild);
+    }
+}
+
+int main()
+{
+    char postfix[] = "ab*cd/-";
+    Tptr expressionTree = createExpression(postfix);
+
+    if (expressionTree != NULL)
+    {
+        printf("In-Order Traversal of the Expression Tree: ");
+        inOrderTraversal(expressionTree);
+        printf("\n");
+    }
+
+    return 0;
+}
diff --git a/DS/C/Lab/Week11/levelOrder.c b/DS/C/Lab/Week11/levelOrder.c
new file mode 100644
index 0000000..c94d432
--- /dev/null
+++ b/DS/C/Lab/Week11/levelOrder.c
@@ -0,0 +1,135 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX 100
+
+typedef struct TNode *Tptr;
+typedef struct TNode {
+    int data;
+    Tptr leftchild;
+    Tptr rightchild;
+} TNode;
+
+typedef struct {
+    Tptr key;
+} element;
+
+element Q[MAX];
+int r = -1;
+int f = -1;
+
+element dequeue() {
+    element ret = {NULL};
+    if (f != r) {
+        f++;
+        ret = Q[f];
+    }
+    return ret;
+}
+
+void enqueue(element e) {
+    if (r < MAX - 1) {  // Check if the queue is not full
+        r++;
+        Q[r] = e;
+    } else {
+        printf("Queue is full\n");
+    }
+}
+
+// Create nodes in the tree
+Tptr createNode(int val) {
+    Tptr temp = (Tptr)malloc(sizeof(TNode));
+    if (temp) {
+        temp->data = val;
+        temp->leftchild = temp->rightchild = NULL;
+    }
+    return temp;
+}
+
+// Create the binary search tree
+void createBST(Tptr *root) {
+    int N, i, val;
+    Tptr current, previous;
+
+    printf("Enter the number of nodes: ");
+    scanf("%d", &N);
+
+    for (i = 0; i < N; i++) {
+        printf("Enter a unique value: ");
+        scanf("%d", &val);
+
+        Tptr temp = createNode(val);
+        if (!temp) {
+            printf("Memory allocation failed\n");
+            return;
+        }
+
+        if (!*root) {
+            *root = temp;
+        } else {
+            current = *root;
+            previous = NULL;
+            int isDuplicate = 0; // Flag for duplicate
+
+            while (current) {
+                previous = current;
+                if (val < current->data) {
+                    current = current->leftchild;
+                } else if (val > current->data) {
+                    current = current->rightchild;
+                } else {
+                    printf("Duplicate. Will only be printed for first occurence.\n");
+                    isDuplicate = 1; // Set flag if duplicate found
+                    break; // Exit loop
+                }
+            }
+
+            if (!isDuplicate) {
+                if (val < previous->data) {
+                    previous->leftchild = temp;
+                } else {
+                    previous->rightchild = temp;
+                }
+            } else {
+                free(temp); // Free memory for duplicate node
+            }
+        }
+    }
+}
+
+// Print in level order
+void levelOrderTraversal(Tptr current) {
+    if (current == NULL) {
+        return;
+    }
+
+    element b;
+    b.key = current;
+    enqueue(b);
+
+    while (f != r) { // While the queue is not empty
+        Tptr currentNode = dequeue().key;
+        printf("%d ", currentNode->data);
+
+        if (currentNode->leftchild != NULL) {
+            b.key = currentNode->leftchild;
+            enqueue(b);
+        }
+
+        if (currentNode->rightchild != NULL) {
+            b.key = currentNode->rightchild;
+            enqueue(b);
+        }
+    }
+}
+
+int main() {
+    Tptr root = NULL;
+
+    createBST(&root);
+
+    printf("Level Order Traversal: ");
+    levelOrderTraversal(root);
+    printf("\n");
+
+    return 0;
+}