How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push,pop and min should all operate in O(1) time.

File:StackBox.java
---------------------------------------------------------------------------------------------------
package org.developersbrain.solutions;

class Student{
String studentName;
int   totalMarks;
String grade;

Student(String studentName,int totalMarks,String grade){
this.studentName = studentName;
this.totalMarks  = totalMarks;
this.grade       = grade;
}

public int hashCode(){
return totalMarks;
}

public String toString(){
System.out.println("Student Name :"+this.studentName);
System.out.println("Total Marks :"+this.totalMarks);
System.out.println("Grade :"+this.grade);
System.out.println();
System.out.println("-------------------------------------------");
return "";
}
}

class StackNode<ELEMENT>{
StackNode<ELEMENT> next;
ELEMENT e;
    ELEMENT min;
StackNode(ELEMENT e){
this.e = e;
next = null;
}
}
public class StackBox<ELEMENT> {
StackNode<ELEMENT> top;

StackBox(){
top=null;
}

void push(ELEMENT e){
StackNode<ELEMENT> snode=new StackNode<ELEMENT>(e);
if(top==null){
top = snode;
top.min=top.e;
}else{
if(snode.e.hashCode()<top.min.hashCode()){
snode.min=snode.e;
}else{
snode.min=top.min;
}
snode.next =top;
top=snode;
}
}

void pop(){
StackNode<ELEMENT> pNode=top;
if(pNode==null){
System.out.println("Stack Empty!");
}else{
System.out.println(pNode.e.toString());
top=top.next;
}
}

void min(){
System.out.println(top.min.toString());
}

void printStack(){
StackNode<ELEMENT> pNode=top;
while(pNode!=null){
pNode.e.toString();
pNode=pNode.next;
}
}
}

File:MainClass.java

-----------------------------------------------------------------------------------------

package org.developersbrain.solutions;

import java.io.IOException;

public class MainClass {

public static void main(String[] args) throws IOException{

StackBox<Student> sb=new StackBox<Student>();

sb.push(new Student("Student1",400,"B"));

sb.push(new Student("Student2",450,"A"));

sb.push(new Student("Student3",420,"B"));

sb.push(new Student("Student4",440,"B"));

sb.push(new Student("Student5",460,"A"));

System.out.println("Print Stack elements");

System.out.println("---------------------------------------------");

sb.printStack();

System.out.println();

System.out.println("Student Who scored the least score");

System.out.println("---------------------------------------------");

sb.min();

}

}

Program Output:

------------------------------------------------------------------------------------------------

Print Stack elements

---------------------------------------------

Student Name :Student5

Total Marks :460

Grade :A

-------------------------------------------

Student Name :Student4

Total Marks :440

Grade :B

-------------------------------------------

Student Name :Student3

Total Marks :420

Grade :B

-------------------------------------------

Student Name :Student2

Total Marks :450

Grade :A

-------------------------------------------

Student Name :Student1

Total Marks :400

Grade :B

-------------------------------------------

Student Who scored the least score

---------------------------------------------

Student Name :Student1

Total Marks :400

Grade :B

-------------------------------------------