Completed Pre Course 1

.vscode/c_cpp_properties.json

@@ -0,0 +1,25 @@
+{
+    "configurations": [
+        {
+            "name": "Mac",
+            "includePath": [
+                "${workspaceFolder}/**"
+            ],
+            "defines": [],
+            "cStandard": "c17",
+            "cppStandard": "c++14",
+            "intelliSenseMode": "macos-clang-arm64"
+        },
+        {
+            "name": "Mac",
+            "includePath": [
+                "${workspaceFolder}/**"
+            ],
+            "defines": [],
+            "cStandard": "c17",
+            "cppStandard": "c++14",
+            "intelliSenseMode": "macos-clang-arm64"
+        }
+    ],
+    "version": 4
+}

.vscode/tasks.json

@@ -0,0 +1,29 @@
+{
+    "tasks": [
+        {
+            "type": "cppbuild",
+            "label": "C/C++: clang++ build active file",
+            "command": "/usr/bin/clang++",
+            "args": [
+                "-fcolor-diagnostics",
+                "-fansi-escape-codes",
+                "-g",
+                "${file}",
+                "-o",
+                "${fileDirname}/${fileBasenameNoExtension}"
+            ],
+            "options": {
+                "cwd": "${fileDirname}"
+            },
+            "problemMatcher": [
+                "$gcc"
+            ],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            },
+            "detail": "Task generated by Debugger."
+        }
+    ],
+    "version": "2.0.0"
+}

Exercise_1.cpp

@@ -1,3 +1,6 @@
+// Time Complexity = O(1) ; fixed number of steps
+// Space Complexity = O(1) ; fixed size of the array
+
 #include <bits/stdc++.h> 
 
 using namespace std; 
@@ -12,7 +15,7 @@ class Stack {
 public: 
     int a[MAX]; // Maximum size of Stack 
 
-    Stack() { //Constructor here } 
+    Stack() { top = -1; } 
     bool push(int x); 
     int pop(); 
     int peek(); 
@@ -21,24 +24,45 @@ class Stack {
 
 bool Stack::push(int x) 
 { 
-    //Your code here
-    //Check Stack overflow as well
+    if (top == MAX - 1){
+        return false;
+    }
+    else{
+        top = top + 1;
+        a[top] = x;
+        return true;
+    }
 } 
 
 int Stack::pop() 
 { 
-    //Your code here
-    //Check Stack Underflow as well 
+    if (top == -1){
+        return -1;
+    }
+    else{
+        int temp = a[top];
+        top--;
+        return temp;
+    }
 } 
 int Stack::peek() 
 { 
-    //Your code here
-    //Check empty condition too
+    if (top == -1){
+        return -1;
+    }
+    else {
+        return a[top];
+    }
 } 
 
 bool Stack::isEmpty() 
 { 
-    //Your code here 
+    if (top == -1){
+        return true;
+    }
+    else{
+        return false;
+    }
 } 
 
 // Driver program to test above functions 

Exercise_2.cpp

@@ -18,22 +18,43 @@ StackNode* newNode(int data)
 
 int isEmpty(StackNode* root) 
 { 
-    //Your code here 
+    if(root == NULL){
+        return 1;
+    }
+    else{
+        return 0;
+    }
 } 
 
 void push(StackNode** root, int data) 
 { 
-    //Your code here 
+    StackNode* temp = newNode(data);
+    temp->next = *root;
+    *root = temp;
 } 
 
 int pop(StackNode** root) 
 { 
-    //Your code here 
+   if (*root == NULL){
+    return -1;
+   }
+   else{
+    StackNode* temp = *root;
+    int popped = temp->data;
+    *root = temp->next;
+    delete temp;
+    return popped;
+   }
 } 
 
 int peek(StackNode* root) 
 { 
-    //Your code here 
+    if(root == NULL){
+        return -1;
+    }
+    else{
+        return root->data;
+    }
 } 
 
 int main() 

Exercise_3.cpp

@@ -14,55 +14,58 @@ to the head of a list and an int, inserts
 a new node on the front of the list. */
 void push(Node** head_ref, int new_data)  
 {  
-    /* 1. allocate node */ 
-
-    /* 2. put in the data */  
-
-    /* 3. Make next of new node as head */ 
-
-    /* 4. move the head to point to the new node */
+    Node* node = new Node();
+    node->data = new_data;
+    node->next = *head_ref;
+    *head_ref = node;
 }  
 
 /* Given a node prev_node, insert a new node after the given  
 prev_node */
 void insertAfter(Node* prev_node, int new_data)  
 {  
-    /*1. check if the given prev_node is NULL */ 
-
-    /* 2. allocate new node */ 
-
-    /* 3. put in the data */ 
-
-    /* 4. Make next of new node as next of prev_node */
-
-    /* 5. move the next of prev_node as new_node */ 
+    if(prev_node == NULL){
+        return;
+    }
+    else{
+        Node* node = new Node();
+        node->data = new_data;
+        node->next = prev_node->next;
+        prev_node->next = node;
+    }
 }  
 
 /* Given a reference (pointer to pointer) to the head  
 of a list and an int, appends a new node at the end */
 void append(Node** head_ref, int new_data)  
 {  
-    /* 1. allocate node */ 
-
-    /* 2. put in the data */ 
-
-    /* 3. This new node is going to be  
-    the last node, so make next of  
-    it as NULL*/  
-
-    /* 4. If the Linked List is empty, 
-    then make the new node as head */
-
-    /* 5. Else traverse till the last node */
-
-    /* 6. Change the next of last node */ 
+    Node* new_node = new Node();
+
+    new_node->data = new_data;
+    new_node->next = NULL;
+
+    if(*head_ref == NULL){
+        *head_ref = new_node;
+        return;
+    }
+
+    Node* last = *head_ref;
+
+    while(last->next != NULL){
+        last = last->next;
+    }
+
+    last->next = new_node;
 }  
 
 // This function prints contents of 
 // linked list starting from head  
 void printList(Node *node)  
 {  
-    //Your code here
+    while(node != NULL){
+        cout << node->data << " ";
+        node = node->next;
+    }
 }  
 
 /* Driver code*/