100DaysofDSA

Things I learned in: Day_12

Note: use the github provided TOC for navigaing.

Stack Data structure:

It follows LIFO order, which means Last in first out. Whcih means that the element that had been inserted last will come out first. Here we add element from the top and remove element from the top.

class Stack{
private:
    vector<int> v;    
public:
    // pushes elements at the back of the vector
    void push(int data){            
        v.push_back(data);
    }
    // check if the stack is empty or not
    bool empty(){
        return v.size()==0;     // if the size of the stack(here its the vector) is zero then the stack is empty
    }
    // insert element at the back
    void pop(){
        if(!empty()){
             v.pop_back();
        }
    }
    // access element from the back, for the stack it the top most element
    int top(){
        return v[v.size()-1];
    }
};

int main() {
    Stack s;

    for(int i=1;i<=5;i++){
        s.push(i*i);
    }
    //Try to print the content of the stack by popping each element
    while(!s.empty()){
        cout<<s.top()<<endl;
        s.pop();
    }
    

return 0;
}

Using template for creating the class:

• it is a stack of multiple data type, means if you do Stack<int,char> S this means we have a stack that can hold integer type as well as charecter type data. ```cpp // template<typename T,typename U> template class Stack{ private: vector v; //vector v2; public: void push(T data){ v.push_back(data); } bool empty(){ return v.size()==0; } void pop(){ if(!empty()){ v.pop_back(); } } T top(){ return v[v.size()-1]; } };

int main() { // Stack<char,int> s; Stack s;

for(int i=65;i<=70;i++){
    s.push(i);
}
//Try to print the content of the stack by popping each element
while(!s.empty()){
    cout<<s.top()<<endl;
    s.pop();
}
return 0; } ```

Stack STL:

• mystack1.swap(mystack2): swaps two stacks.

    before swaping:
    mystack1 = 4 3 2 1 
    mystack2 = 9 7 5 3 
    After swaping:
    mystack1 = 9 7 5 3 
    mystack2 = 4 3 2 1 
  

• mystack.size(): gives size of the stack.
• mystack.pop()
• mystack.push()
• mystack.top()
• mystack.empty()

#include <iostream>
#include<stack>
using namespace st;

int main(int argc, char const *argv[])
{
    stack<int> s;
    for(int i=0;i<=5;i++){
        s.push(i);      // push is used to push an element in the stack 

    }
    // loop
    while(!s.empty()){   // using empty to check that the stack is empty or not
        
        cout<<s.top()<<", "; // top is used to get the top most element
        s.pop();             // pop is used to pop out a element(we know it 
                             // works in LIFO order)
    }
    return 0;
}