String Palindrome:
bool palindrome(string s) {
    string r=s;
    reverse(s.begin(),s.end());
    if(s==r) return true;
    else return false;
}

Binary Search:
bool bsearch(int ar[], int n, int e) {
    int l = 0, h = n - 1;
    while (h - l > 1) {
        int mid = (h + l) / 2;
        if (ar[mid] < e) l = mid + 1;
        else h = mid;
    }
    return (ar[l] == e || ar[h] == e);
}

Bubble Sort:
void bubblesort(int ar[], int n) {
    for (int i = 0; i < n - 1; ++i) {
        for (int j = 0; j < n - i - 1; ++j) {
            if (ar[j] > ar[j + 1])
                swap(ar[j], ar[j + 1]);
        }
    }
}

Radix Sort:
void radixsort(int ar[], int n) {
    int mx = *max_element(ar, ar + n);
    for (int exp = 1; mx / exp > 0; exp *= 10) {
        int op[n], cnt[10]{};
        for (int i = 0; i < n; ++i) ++cnt[(ar[i] / exp) % 10];
        for (int i = 1; i < 10; ++i) cnt[i] += cnt[i - 1];
        for (int i = n - 1; i >= 0; --i) op[--cnt[(ar[i] / exp) % 10]] = ar[i];
        copy(op, op + n, ar);
    }
}

Bucket Sort:
void bubblesort(int ar[], int n) {
    for (int i = 0; i < n - 1; ++i) {
        for (int j = 0; j < n - i - 1; ++j) {
            if (ar[j] > ar[j + 1])
                swap(ar[j], ar[j + 1]);
        }
    }
}
void bucketsort(int ar[], int n) {
    int buck = (*max_element(ar, ar + n) / 100) + 1;
    vector<int> bucket[buck];
    for (int i = 0; i < n; ++i) bucket[ar[i] / 100].push_back(ar[i]);
    for (int i = 0; i < buck; ++i) bubblesort(bucket[i]);
    int k = 0;
    for (auto& i : bucket) for (auto& j : i) ar[k++] = j;
}

Stack using array:
#include <bits/stdc++.h>
using namespace std;
int stk[100], top = -1;
void push(int val) {
    if (top >= 100 - 1) cout << "Stack Overflow" << '\n';
    else stk[++top] = val;
}
void pop() {
    if (top <= -1) cout << "Stack Underflow" << '\n';
    else cout << "The popped element is " << stk[top--] << '\n';
}
void display() {
    if (top >= 0) {
        cout << "Stack elements are: ";
        for (int i = top; i >= 0; --i) cout << stk[i] << ' ';
    }
    else cout << "Stack is empty!!!";
    cout << '\n';
}
int main() {
    cout << "1) Push in stack" << '\n';
    cout << "2) Pop from stack" << '\n';
    cout << "3) Display stack" << '\n';
    cout << "4) Exit" << '\n';
    int ch;
    do {
        cout << "Enter choice: "; cin >> ch;
        switch (ch) {
        case 1: {
            cout << "Enter value to be pushed: " << '\n';
            int val; cin >> val; push(val); break;
        }
        case 2: {
            pop(); break;
        }
        case 3: {
            display(); break;
        }
        case 4: {
            cout << "Exit" << '\n'; break;
        }
        default:
            cout << "Invalid Choice" << '\n';
        }
    } while (ch != 4);
    return 0;
}

Queue using array:
#include <bits/stdc++.h>
using namespace std;
int q[100], front = -1, rear = -1;
void insert() {
    int val;
    if (rear == 100 - 1) cout << "Queue Overflow" << '\n';
    else {
        if (front == -1) front = 0;
        cout << "Insert the element in queue: " << '\n';
        cin >> val; q[++rear] = val;
    }
}
void remove() {
    if (front == -1 || front > rear) cout << "Queue Underflow ";
    else cout << "Element removed from queue is: " << q[front++] << '\n';
}
void display() {
    if (front == -1) cout << "Queue is empty" << '\n';
    else {
        cout << "Queue elements are : ";
        for (int i = front; i <= rear; i++) cout << q[i] << " ";
        cout << '\n';
    }
}
int main() {
    cout << "1) Insert element to queue" << '\n';
    cout << "2) remove element from queue" << '\n';
    cout << "3) Display all the elements of queue" << '\n';
    cout << "4) Exit" << '\n';
    int ch;
    do {
        cout << "Enter your choice : " << '\n';
        cin >> ch;
        switch (ch) {
        case 1: insert(); break;
        case 2: remove(); break;
        case 3: display(); break;
        case 4: cout << "Exit" << '\n'; break;
        default: cout << "Invalid choice" << '\n';
        }
    } while (ch != 4);
    return 0;
}

Linked list:
#include <bits/stdc++.h>
using namespace std;
class Node {
public:
    int data; Node* next;
    Node() {
        data = 0; next = NULL;
    }
    Node(int data) {
        this->data = data; this->next = NULL;
    }
};
class Linkedlist {
    Node* head;
public:
    Linkedlist() { head = NULL; }
    void insert();
    void display();
    void remove();
};
void Linkedlist::remove() {
    cout << "Enter the element to remove: ";
    int ele; cin >> ele;
    Node* tmp1 = head, * tmp2 = NULL;
    int len = 0;
    if (head == NULL) {
        cout << "List is empty." << '\n'; return;
    }
    while (tmp1 != NULL) {
        tmp1 = tmp1->next; ++len;
    }
    if (len < ele) {
        cout << "Index out of range" << '\n'; return;
    }
    tmp1 = head;
    if (ele == 1) {
        head = head->next;
        delete tmp1; return;
    }
    while (--ele) {
        tmp2 = tmp1; tmp1 = tmp1->next;
    }
    tmp2->next = tmp1->next;
    delete tmp1;
}
void Linkedlist::insert() {
    cout << "Enter the element to insert: ";
    int data; cin >> data;
    Node* newNode = new Node(data);
    if (head == NULL) {
        head = newNode; return;
    }
    Node* tmp = head;
    while (tmp->next != NULL) tmp = tmp->next;
    tmp->next = newNode;
}
void Linkedlist::display() {
    cout << "Elements of the list are: ";
    Node* tmp = head;
    if (head == NULL) {
        cout << "List is empty\n"; return;
    }
    while (tmp != NULL) {
        cout << tmp->data << ' '; tmp = tmp->next;
    }
    cout << '\n';
}
int main() {
    Linkedlist list;
    cout << "1) Insert element to list" << '\n';
    cout << "2) Remove element from list" << '\n';
    cout << "3) Display all the elements of list" << '\n';
    cout << "4) Exit" << '\n';
    int ch;
    do {
        cout << "Enter your choice : " << '\n';
        cin >> ch;
        switch (ch) {
        case 1: list.insert(); break;
        case 2: list.remove(); break;
        case 3: list.display(); break;
        case 4: cout << "Exit" << '\n'; break;
        default: cout << "Invalid choice" << '\n';
        }
    } while (ch != 4);
    return 0;
}

BST:
#include <bits/stdc++.h>
using namespace std;
class Node {
public:
    int val; Node* left, * right;
    Node(int val): val(val), left(NULL), right(NULL) { }
};
void insert(Node*& root) {
    cout << "Enter the element to insert: ";
    int key; cin >> key;
    Node* node = new Node(key);
    if (!root) {
        root = node; return;
    }
    Node* prev = NULL, * temp = root;
    while (temp) {
        if (temp->val > key) {
            prev = temp; temp = temp->left;
        }
        else if (temp->val < key) {
            prev = temp; temp = temp->right;
        }
    }
    if (prev->val > key) prev->left = node;
    else prev->right = node;
}
void inorder(Node* node) {
    if (node == NULL) return;
    inorder(node->left);
    cout << node->val << ' ';
    inorder(node->right);
}
void preorder(Node* node) {
    if (node == NULL) return;
    cout << node->val << ' ';
    preorder(node->left);
    preorder(node->right);
}
void postorder(Node* node) {
    if (node == NULL) return;
    postorder(node->left);
    postorder(node->right);
    cout << node->val << ' ';
}
int main() {
    Node* root = NULL;
    cout << "1) Insert element to BST" << '\n';
    cout << "2) Display inorder traversal" << '\n';
    cout << "3) Display preorder traversal" << '\n';
    cout << "4) Display postorder traversal" << '\n';
    cout << "5) Exit" << '\n';
    int ch;
    do {
        cout << "Enter your choice : " << '\n';
        cin >> ch;
        switch (ch) {
        case 1: insert(root); break;
        case 2: inorder(root); break;
        case 3: preorder(root); break;
        case 4: postorder(root); break;
        case 5: cout << "Exit" << '\n'; break;
        default: cout << "Invalid choice" << '\n';
        }
    } while (ch != 5);
    return 0;
}