This card game begins with an empty deck.
There are following types of operations in the game :
Add X : Add a card with number X onto the top of the deck pile.
Remove : Remove the TopMost card from the deck pile.
CallMin : Find the minimum numbered card from the deck pile.
CallMax : Find the maximum numbered card from the deck pile.
You are given a sequence of operations of the game and your task is to write a program to play the game.
NOTE : You are expected to use the stack data structure only to get optimal solution. Other solutions may not be efficient enough.
INPUT
First line contains N the number of operations.
Next N lines each contain one operation each : "Add X", "Remove", "CallMax" or "CallMin" where X can be any non-negative integer.
OUTPUT
Output the minimum element whenever CallMin command is given, the maximum element whenever CallMax command is given, or "Invalid" whenever CallMin/CallMax/Remove command is given on an empty stack.
1
3
0
3
1
Invalid
Invalid
Solution :import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
import java.util.ArrayList;
import java.util.List;
public class Solution {
List<Node> items;
public void push(int num) {
if (items == null) {
items = new ArrayList<Node>();
}
Node node = new Node(num);
if (items.size() > 0) {
node.min = Math.min(items.get(items.size() - 1).min, num);
node.max = Math.max(items.get(items.size() - 1).max, num);
} else {
node.min = num;
node.max = num;
}
items.add(node);
}
public Node pop() {
Node popThis = null;
if (items != null && items.size() > 0) {
popThis = this.items.get(items.size() - 1);
items.remove(items.size() - 1);
}
else
System.out.println("Invalid");
return popThis;
}
public int getMin() {
if (items != null && items.size() > 0) {
int min = this.items.get(items.size() - 1).min;
System.out.println(min);
return min;
}
else
System.out.println("Invalid");
return -1;
}
public int getMax() {
if (items != null && items.size() > 0) {
int max = this.items.get(items.size() - 1).max;
System.out.println(max);
return max;
}
else
System.out.println("Invalid");
return -1;
}
public static void main(String args[]) {
Solution stack = new Solution();
Scanner sc = new Scanner(System.in);
int a = sc.nextInt();
while(a>0)
{
String s=sc.next();
int tem;
if(s.equals("Add")){
tem = sc.nextInt();
stack.push(tem);
}
else if(s.equals("CallMin")){
stack.getMin();
}
else if(s.equals("CallMax")){
stack.getMax();
}
else if(s.equals("Remove")){
stack.pop();
}
a--;
}
}
}
class Node {
int data;
int min;
int max;
public Node(int data) {
super();
this.data = data;
}
public Node() {
super();
}
}
