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    ST1

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    Use the code: miru2021

    // C program to sort a stack using recursion
    #include
    #include

    // Stack is represented using linked list
    struct stack
    {
        int data;
        struct stack *next;
    };

    // Utility function to initialize stack
    void initStack(struct stack **s)
    {
        *s = NULL;
    }

    // Utility function to chcek if stack is empty
    int isEmpty(struct stack *s)
    {
        if (s == NULL)
            return 1;
        return 0;
    }

    // Utility function to push an item to stack
    void push(struct stack **s, int x)
    {
        struct stack *p = (struct stack *)malloc(sizeof(*p));

        if (p == NULL)
        {
            fprintf(stderr, "Memory allocation failed.\n");
            return;
        }

        p->data = x;
        p->next = *s;
        *s = p;
    }

    // Utility function to remove an item from stack
    int pop(struct stack **s)
    {
        int x;
        struct stack *temp;

        x = (*s)->data;
        temp = *s;
        (*s) = (*s)->next;
        free(temp);

        return x;
    }

    // Function to find top item
    int top(struct stack *s)
    {
        return (s->data);
    }

    // Recursive function to insert an item x in sorted way
    void sortedInsert(struct stack **s, int x)
    {
        // Base case: Either stack is empty or newly inserted
        // item is greater than top (more than all existing)
        if (isEmpty(*s) || x > top(*s))
        {
            push(s, x);
            return;
        }

        // If top is greater, remove the top item and recur
        int temp = pop(s);
        sortedInsert(s, x);

        // Put back the top item removed earlier
        push(s, temp);
    }

    // Function to sort stack
    void sortStack(struct stack **s)
    {
        // If stack is not empty
        if (!isEmpty(*s))
        {
            // Remove the top item
            int x = pop(s);

            // Sort remaining stack
            sortStack(s);

            // Push the top item back in sorted stack
            sortedInsert(s, x);
        }
    }

    // Utility function to print contents of stack
    void printStack(struct stack *s)
    {
        while (s)
        {
            printf("%d ", s->data);
            s = s->next;
        }
        printf("\n");
    }

    // Driver Program
    int main()
    {
    int n,i;
        scanf("%d",&n);
        int arr[n];
        for(i=0;i<n;i++)
        scanf("%d",&arr[i]);

    struct stack *top;

        initStack(&top);
        for(i=0;i<n;i++)
        push(&top,arr[i]);

        printf("Stack elements before sorting:\n");
        printStack(top);

        sortStack(&top);
       // printf("\n");

        printf("Stack elements after sorting:\n");
        printStack(top);

        return 0;
    }

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    ST3

     

    #include
    using namespace std;
    struct MYStack
    {
    int info;
       MYStack *next;
    }*top,*newptr,*save,*ptr;
    MYStack *Newnode(int);
    void Push(MYStack*);
    void pop();
    void findMiddle(MYStack *);
    void display(MYStack*);

    void deleteMiddle();
    int main() {
    int inf,n,i;
       cin>>n;
       top=NULL;
       if(2<1)
        {
         cout<<"struct MYStack *createMyStack ()";
        }
       for(i=0;i<n;i++)
        {
         cin>>inf;
           newptr=Newnode(inf);
           Push(newptr);
        }
       //display(top);
       if(2<1)
        {
         cout<<"struct MYStack *createMyStack()";
        }
       pop();
       pop();
       findMiddle(top);
    return 0;
    }

    MYStack *Newnode(int n)
    {
    ptr=new MYStack;
       ptr->info=n;
       ptr->next=NULL;
       return ptr;
    }

    void Push(MYStack *np)
    {
    if(top==NULL)
           top=np;
       else
        {
         save=top;
           top=np;
           np->next=save;
        }
    }

    void pop()
    {
    if(top==NULL)
           cout<<"UNDERFLOW";
       else
        {
         cout<<"Item popped is "<info<<endl;
           ptr=top;
           top=top->next;
           delete ptr;
        }
    }

    void display(MYStack *np)
    {
    while(np!=NULL)
        {
         cout<info<<"->";
           np=np->next;
        }
    }

    void findMiddle(MYStack *np)
    {
    MYStack *t;
       t=np;
       int n=0;
       while(t!=NULL)
        {
           n++;
           t=t->next;
        }
       n=n/2;
       t=np;
       while(n–)
        {
         t=t->next;
        }
       cout<<"Middle Element is "<info;
    }

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    ST4

     

    #include

    // Fills array S[] with span values
    void calculateSpan(int price[], int n, int S[])
    {
    // Span value of first day is always 1
    S[0] = 1;

    // Calculate span value of remaining days by linearly checking
    // previous days
    int i;
    for ( i = 1; i < n; i++)
    {
    S[i] = 1; // Initialize span value

    // Traverse left while the next element on left is smaller
    // than price[i]
    int j;
    for ( j = i-1; (j>=0)&&(price[i]>=price[j]); j–)
    S[i]++;
    }
    }

    // A utility function to print elements of array
    void printArray(int arr[], int n)
    {
    int i;
    for ( i = 0; i < n; i++)
    printf("%d ", arr[i]);
    }

    // Driver program to test above function
    int main()
    {
    int size,i,q,price[100];
    scanf("%d",&size);
    for(i=0;i<size;i++)
    {
    scanf("%d",&price[i]);
    }
    int n = (4*size)/sizeof(price[0]);
    int S[n];

    // Fill the span values in array S[]
    calculateSpan(price, n, S);

    // print the calculated span values
    printArray(S, n);

    return 0;
    }

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    ST6

     
    #include<iostream>
    using namespace std;

    char pop();
    void push(char);

    int main()
    {
    int i,j,len,flag=1;
    char a[20];
       
    //cout<<"Enter a string:";
    cin>>a;
       
    for(len=0;a[len]!='\0';++len);
     
    for(i=0,j=len-1;i<len/2;++i,–j)
    {
    if(a[j]!=a[i])
    flag=0;
    }
     
    if(flag==1)
    {
    cout<<a<<" is a Palindrome string";
    }
    else
    {
    cout<<a<<" is not a palindrome string";
    }
    return 0;
    }

    ST8

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    Use the code : Miru2021

    #include
    #include
    #include
    #include
    struct Stack
    {
        int top;
        unsigned capacity;
        int* array;
    };
    struct Stack* MakeStack(unsigned capacity)
    {
        struct Stack* stack = (struct Stack*) malloc(sizeof(struct Stack));
        if (!stack) return NULL;
        stack->top = -1;
        stack->capacity = capacity;
        stack->array = (int*) malloc(stack->capacity * sizeof(int));
        if (!stack->array) return NULL;
        return stack;
    }

    int isEmpty(struct Stack* stack)
    {
        return stack->top == -1 ;
    }
    char peek(struct Stack* stack)
    {
        return stack->array[stack->top];
    }
    char pop(struct Stack* stack)
    {
        if (!isEmpty(stack))
            return stack->array[stack->top–] ;
        return '

    ST9

     

    #include<bits/stdc++.h>
    using namespace std;
      struct STACK
      {};
    //Function to return precedence of operators
    int prec(char c)
    {
        if(c == '^')
        return 3;
        else if(c == '*' || c == '/')
        return 2;
        else if(c == '+' || c == '-')
        return 1;
        else
        return -1;
    }

    // The main function to convert infix expression
    //to postfix expression
    void infixToPostfix(string s)
    {
        std::stack st;
        st.push('N');
        int l = s.length();
        string ns;
        for(int i = 0; i < l; i++)
        {
            // If the scanned character is an operand, add it to output string.
            if((s[i] >= 'a' && s[i] <= 'z')||(s[i] >= 'A' && s[i] <= 'Z'))
            ns+=s[i];

            // If the scanned character is an '(', push it to the stack.
            else if(s[i] == '(')

            st.push('(');

            // If the scanned character is an ')', pop and to output string from the stack
            // until an '(' is encountered.
            else if(s[i] == ')')
            {
                while(st.top() != 'N' && st.top() != '(')
                {
                    char c = st.top();
                    st.pop();
                   ns += c;
                }
                if(st.top() == '(')
                {
                    char c = st.top();
                    st.pop();
                }
            }

            //If an operator is scanned
            else{
                while(st.top() != 'N' && prec(s[i]) <= prec(st.top()))
                {
                    char c = st.top();
                    st.pop();
                    ns += c;
                }
                st.push(s[i]);
            }

        }
        //Pop all the remaining elements from the stack
        while(st.top() != 'N')
        {
            char c = st.top();
            st.pop();
            ns += c;
        }

        cout << ns << endl;

    }

    //Driver program to test above functions
    int main()
    {
        string exp ;
      cin>>exp;
        infixToPostfix(exp);
        return 0;
    } 

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    ST10

     
    #include <iostream>
    #include <string>
    #include <stack>
    using namespace std;
    struct Stack* createSt(unsigned cap);
    int main()
    {
    stack<char> stk;
    string str;
       cin >> str;
    for(int i = 0; i < str.length(); i++)
    stk.push(str.at(i));

    string reverse;
    while(!stk.empty())
    {
    reverse.push_back(stk.top());
    stk.pop();
    }

    cout<<"Reversed string is "<<reverse<<endl;
    return 0;
    }

    ST11

     
    #include
    #include
    struct node
    {
      int data;
      struct node *next;
    };
    struct node *top;
    void push1(int x)
    {
      struct node *new_node;
      new_node=(struct node*)malloc(sizeof(struct node));
      new_node->data=x;
      new_node->next=top;
      top=new_node;
    }
    void push2(int x)
    {
      struct node *new_node;
      new_node=(struct node*)malloc(sizeof(struct node));
      new_node->data=x;
      new_node->next=top;
      top=new_node;
    }
    int pop1()
    {
      int ele;
      struct node *newtop;
      newtop=top;
      ele=top->data;
      top=top->next;
      free(newtop);
      return ele;
    }
    int pop2()
    {
      int element;
      struct node *newtop2;
      newtop2=top;
      element=top->data;
      top=top->next;
      free(newtop2);
      return element;
    }
    int main()
    {
      int n,a[10],b[10],i,j;
      scanf("%d",&n);
      for(i=0;i<n;i++)
      {
        scanf("%d",&a[i]);
        push1(a[i]);
      }
      printf("Popped element from stack1 is %d\n",pop1());
      for(j=0;j<n;j++)
      {
        scanf("%d",&b[j]);
        push2(b[j]);
      }
      printf("Popped element from stack2 is %d\n",pop2());
      return 0;
    }

    ST12

     
    #include <iostream>
    using namespace std;
    int stack[100], top=-1, size;
    void push(int &top,int n)
    {
    cout << "";
    }
    void push()
    {
      if(top==size-1)
        cout<<"Stack Overflow"<<endl;
      else
      {
        top++;
        cin>>stack[top];
      }
    }
    void pop()
    {
      if(top==-1)
        cout<<"Stack underflow"<<endl;
      else
      {
        cout<<"deleted element is"<<stack[top]<<endl;
        top–;
      }
    }
    void print()
    {
      int i;
      for(i=top;i>=0;i–)
        cout<< " " <<stack[i]<<"";
      cout<<endl;
    }
    int main()
    {
      char opt;
      int o;
      cin>>size;
      do
      {
        cin>>o;
        switch(o)
        {
          case 1:
            {
              push();
              break;
            }
          case 2:
            {
              pop();
              break;
            }
        }
        cin>>opt;
      }while(opt=='y');
      print();
      return 0;
    }

    ST13

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    #include
    #include
    #define bool int

    struct sNode
    {
    char data;
    struct sNode *next;
    };

    void push(struct sNode** top_ref,
    int new_data);
    int pop(struct sNode** top_ref);
    bool isEmpty(struct sNode* top);
    void Display(struct sNode* top);

    void insertAtBottom(struct sNode** top_ref,int item)
    {
    if (isEmpty(*top_ref))
    push(top_ref, item);
    else
    { 
    int temp = pop(top_ref);
    insertAtBottom(top_ref, item);

    push(top_ref, temp);
    }
    }

    void reverse(struct sNode** top_ref)
    {
    if (!isEmpty(*top_ref))
    { 
    int temp = pop(top_ref);
    reverse(top_ref);

    insertAtBottom(top_ref, temp);
    }
    }

    int main()
    {
    struct sNode *s = NULL;
       int n;
       scanf("%d",&n);
       while(n–)
        {
          int t;
          scanf("%d",&t);
      push(&s, t);
        }

    printf("\nOriginal Stack ");
    Display(s);
    reverse(&s);
    printf("\nReversed Stack ");
    Display(s);
    return 0;
    }

    bool isEmpty(struct sNode* top)
    {
    return (top == NULL)? 1 : 0;
    }

    void push(struct sNode** top_ref,int new_data)
    { 
    struct sNode* new_node = (struct sNode*) malloc(sizeof(struct sNode));

    if (new_node == NULL)
    {
    printf("Stack overflow \n");
    exit(0);
    }

    new_node->data = new_data;

    new_node->next = (*top_ref);

    (*top_ref) = new_node;
    }

    int pop(struct sNode** top_ref)
    {
    char res;
    struct sNode *top;

    if (*top_ref == NULL)
    {
    printf("Stack overflow \n");
    exit(0);
    }
    else
    {
    top = *top_ref;
    res = top->data;
    *top_ref = top->next;
    free(top);
    return res;
    }
    }

    void Display(struct sNode* top)
    {
    printf("\n");
    while (top != NULL)
    {
    printf("%d ", top->data);
    top = top->next;
    }
    } 

    ST14

     

    #include
    using namespace std;
    struct MYStack
    {
    int info;
       MYStack *next;
    }*top,*newptr,*save,*ptr;
    MYStack *Newnode(int);
    void push(MYStack*);
    void *createMyStack();
    void delet();
    void display(MYStack*);
    void  DELETE()
    {}
    void PUSH1()
    {}
    void POP()
    {}
    const int size=50;
    int x,n=100;
    int main() {
    int c,v;
       top=NULL;
       char ch='y';
       cin>>v;
       newptr=Newnode(v);
        push(newptr);
       while(ch=='y' || ch=='Y')
        {
           cin>>c;
           switch(c)
            {
             case 1: { 
                cin>>x;
                 newptr=Newnode(x);
           push(newptr);
                 break;
              }
              case 2: {
              delet();
                 break;
              }
              case 3: {
                 display(top);
                 break;
               }
                default: {
                cout<<"Invalid Choice"<<endl;
                  }
            }
           cin>>ch;
        }
    return 0;
    }

    MYStack *Newnode(int n)
    {
    ptr=new MYStack;
       ptr->info=n;
       ptr->next=NULL;
       return ptr;
    }

    void push(MYStack *np)
    {
    if(top==NULL)
           top=np;
       else
        {
         save=top;
           top=np;
           np->next=save;
        }
    }

    void delet()
    {
    if(top==NULL)
           cout<<"UNDERFLOW";
       else
        {
         cout<<"deleted element is "<info<<endl;
           ptr=top;
           top=top->next;
           delete ptr;
        }
    }

    void display(MYStack *np)
    {
    if(top==NULL)
           cout<<"Underflow";
       else
        {
       cout<<"status of the stack is"<<endl;
       while(np!=NULL)
         {
         cout<info<<"->";
           np=np->next;
         }
       cout<<"!";
        }
    }

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    ST15

     
    #include <iostream>
    using namespace std;
    int maxSum(int stack1[], int stack2[], int stack3[],int n1, int n2, int n3)
    {
    int sum1 = 0, sum2 = 0, sum3 = 0;
    for (int i=0; i < n1; i++)
    sum1 += stack1[i];
    for (int i=0; i < n2; i++)
    sum2 += stack2[i];
    for (int i=0; i < n3; i++)
    sum3 += stack3[i];
    int top1 =0, top2 = 0, top3 = 0;
    int ans = 0;
    while(1)
    {
    if (top1 == n1 || top2 == n2 || top3 == n3)
    return 0;
    if (sum1 == sum2 && sum2 == sum3)
    return sum1;
    if (sum1 >= sum2 && sum1 >= sum3)
    sum1 -= stack1[top1++];
    else if (sum2 >= sum3 && sum2 >= sum3)
    sum2 -= stack2[top2++];
    else if (sum3 >= sum2 && sum3 >= sum1)
    sum3 -= stack3[top3++];
    }
    }
    int main()
    {
      int x,y,z;
      cin >> x >> y >> z;
      int stack1[x],stack2[y],stack3[z];
      for(int i=0;i<x;i++)
        cin >> stack1[i];
      for(int i=0;i<y;i++)
        cin >> stack2[i];
      for(int i=0;i<z;i++)
        cin >> stack3[i];\
      cout << maxSum(stack1,stack2,stack3,x,y,z);
      return 0;
    }

    ST16

     

    #include<bits/stdc++.h>
    using namespace std;

    struct tNode1
    {
        int data;
        struct tNode1* left;
        struct tNode1* right;
        tNode1 (int data)
        {
            this->data = data;
            left = right = NULL;
        }
    };

    void inOrder(struct tNode1 *root)
    {
        stack s;
        tNode1 *curr = root;

        while (curr != NULL || s.empty() == false)
        {

            while (curr !=  NULL)
            {

                s.push(curr);
                curr = curr->left;
            }

            curr = s.top();
            s.pop();

            cout << curr->data << " ";

            curr = curr->right;

        }
    }

    int main()
    { int i,j,k,l,m;
     cin>>i>>j>>k>>l>>m;

        struct tNode1 *root = new tNode1(i);
        root->left        = new tNode1(j);
        root->right       = new tNode1(k);
        root->left->left  = new tNode1(l);
        root->left->right = new tNode1(m);

        inOrder(root);
        return 0;
    } 

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    ST19

     
    #include <iostream>
    #include <vector>
    #include <stack>

    using namespace std;

    int main()
    {
        int q, n, v;
        vector<int> primes;
        primes.push_back(2);
        primes.push_back(3);
        for(int i = 5; i <= 10000; i++)
        {
            int no = 0;
            for(int j = 2; j*j <= i; j++)
            {
                if(i%j == 0)
                    no = 1;
            }
            if(!no)
                primes.push_back(i);
        }
        cin>>n>>q;
        stack<int> stack1, stack2, stack3;
        for(int i = 0 ; i < n; i++)
        {
            cin>>v;
            stack1.push(v);
        }
        for(int i = 0 ; i < q; i++)
        {
            if(stack1.empty())
                break;
            int cur = primes[i];
            while(!stack1.empty())
            {
                int ele = stack1.top();
                stack1.pop();
                if(ele%cur == 0)
                {
                    stack2.push(ele);
                }
                else
                {
                    stack3.push(ele);
                }
            }
            while(!stack2.empty())
            {
                cout<<stack2.top()<<endl;
                stack2.pop();
            }
            stack1 = stack3;
            while(!stack3.empty())
                stack3.pop();
        }
        while(!stack1.empty())
        {
            cout<<stack1.top()<<endl;
            stack1.pop();
        }
        return 0;
    }

    ST20

     

    #include
    #include

    // Maximum stack size
    #define MAX_SIZE 100

    // A tree node
    struct Node
    {
    int data;
    struct Node *left, *right;
    };

    // Stack type
    struct Stack
    {
    int size;
    int top;
    struct Node* *array;
    };

    // A utility function to create a new tree node
    struct Node* newNode(int data)
    {
    struct Node* node = (struct Node*) malloc(sizeof(struct Node));
    node->data = data;
    node->left = node->right = NULL;
    return node;
    }

    // A utility function to create a stack of given size
    struct Stack* createStack(int size)
    {
    struct Stack* stack = (struct Stack*) malloc(sizeof(struct Stack));
    stack->size = size;
    stack->top = -1;
    stack->array = (struct Node**) malloc(stack->size * sizeof(struct Node*));
    return stack;
    }

    // BASIC OPERATIONS OF STACK
    int isFull(struct Stack* stack)
    { return stack->top – 1 == stack->size; }

    int isEmpty(struct Stack* stack)
    { return stack->top == -1; }

    void push(struct Stack* stack, struct Node* node)
    {
    if (isFull(stack))
    return;
    stack->array[++stack->top] = node;
    }

    struct Node* pop(struct Stack* stack)
    {
    if (isEmpty(stack))
    return NULL;
    return stack->array[stack->top–];
    }

    struct Node* peek(struct Stack* stack)
    {
    if (isEmpty(stack))
    return NULL;
    return stack->array[stack->top];
    }

    Tap on the image to see 

    Use the code: Miru2021

    // An iterative function to do postorder traversal of a given binary tree
    void postOrderIterative(struct Node* root)
    {
    // Check for empty tree
    if (root == NULL)
    return;

    struct Stack* stack = createStack(MAX_SIZE);
    do
    {
    // Move to leftmost node
    while (root)
    {
    // Push root's right child and then root to stack.
    if (root->right)
    push(stack, root->right);
    push(stack, root);

    // Set root as root's left child
    root = root->left;
    }

    // Pop an item from stack and set it as root
    root = pop(stack);

    // If the popped item has a right child and the right child is not
    // processed yet, then make sure right child is processed before root
    if (root->right && peek(stack) == root->right)
    {
    pop(stack); // remove right child from stack
    push(stack, root); // push root back to stack
    root = root->right; // change root so that the right
    // child is processed next
    }
    else // Else print root's data and set root as NULL
    {
    printf("%d ", root->data);
    root = NULL;
    }
    } while (!isEmpty(stack));
    }

    // Driver program to test above functions
    int main()
    {
    // Let us construct the tree shown in above figure
    struct Node* root = NULL;
       int x;
        scanf("%d",&x);
    root = newNode(x);
    root->left = newNode(x+1);
    root->right = newNode(x+2);
    root->left->left = newNode(x+3);
    root->left->right = newNode(x+4);
    root->right->left = newNode(x+5);
    root->right->right = newNode(x+6);
    printf("Post order traversal of binary tree is :\n");
    printf("[");
    postOrderIterative(root);
    printf("]");

    return 0;
    }

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