Updated stack basic algos 1

Author: Vishal023

Stack/ArrayImplementation.java

@@ -0,0 +1,61 @@
+package SummerTrainingGFG.Stack;
+
+/**
+ * @author Vishal Singh
+ */
+public class ArrayImplementation {
+    static class Stack{
+        private final int size;
+        private final int[] arr;
+        private int top;
+        Stack(int size){
+            this.size = size;
+            arr = new int[size];
+        }
+        void push(int data){
+            if(top == size){
+                System.out.println("Overflow");
+            }
+            else{
+                arr[top] = data;
+                top++;
+            }
+        }
+        int pop(){
+            if(top == 0){
+                System.out.println("Underflow");
+                return -1;
+            }
+            else{
+                int res = arr[top-1];
+                top--;
+                return res;
+            }
+        }
+        void print(){
+            if(top == -1) {
+                System.out.println("No element present");
+            }
+            else{
+                for (int i = 0; i < top; i++) {
+                    System.out.print(arr[i]+" ");
+                }
+                System.out.println("");
+            }
+        }
+    }
+    public static void main(String[] args) {
+        Stack s = new Stack(3);
+        s.push(5);
+        s.push(4);
+        s.push(3);
+        s.print();
+        s.push(31);
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        s.push(1);
+        s.print();
+    }
+}

Stack/BalancedParenthesis.java

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+package SummerTrainingGFG.Stack;
+import java.util.*;
+/**
+ * @author Vishal Singh
+ */
+public class BalancedParenthesis {
+    static boolean check(char a,char b){
+        return (a=='{' && b == '}')||(a=='[' && b == ']')||(a=='(' && b == ')');
+    }
+    static boolean isBalancedParenthesis(String str){
+        Stack<Character> stack = new Stack<>();
+        for (int i = 0; i < str.length(); i++) {
+            if(str.charAt(i) == '{' || str.charAt(i) == '[' || str.charAt(i) == '('){
+                stack.push(str.charAt(i));
+            }
+            else{
+                if(stack.isEmpty()){
+                    return false;
+                }
+                else if(check(str.charAt(i),stack.peek())){
+                    return false;
+                }
+                else{
+                    stack.pop();
+                }
+            }
+        }
+        return stack.empty();
+    }
+    public static void main(String[] args) {
+        String parenthesis = "{[([{}])]}"; // TRUE
+        String parenthesis1 = "{[}]}"; // FALSE
+        System.out.println(isBalancedParenthesis(parenthesis));
+        System.out.println(isBalancedParenthesis(parenthesis1));
+    }
+}

Stack/LinkedListStack.java

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+package SummerTrainingGFG.Stack;
+
+/**
+ * @author Vishal Singh
+ */
+public class LinkedListStack {
+    static class Node{
+        int data;
+        Node next;
+        Node(int data){
+            this.data = data;
+        }
+    }
+    static class List{
+        Node head;
+        void insertEnd(int data){
+            Node temp = new Node(data);
+            temp.next = head;
+            head = temp;
+        }
+        int pop(){
+            if(head == null){
+                return -1;
+            }
+           int data = head.data;
+           head = head.next;
+           return data;
+        }
+        void print(){
+            Node temp = head;
+            while(temp != null){
+                System.out.print(temp.data+" ");
+                temp = temp.next;
+            }
+            System.out.println("");
+        }
+    }
+    static class Stack {
+        private final List list = new List();
+        void push(int data){
+            list.insertEnd(data);
+        }
+        int pop(){
+            int temp = list.pop();
+            return temp;
+        }
+        void print(){
+            list.print();
+        }
+    }
+
+    public static void main(String[] args) {
+        Stack s = new Stack();
+        s.push(5);
+        s.push(4);
+        s.push(3);
+        s.push(31);
+        s.print();
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        System.out.println(s.pop());
+        s.push(1);
+        s.print();
+    }
+}