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advance_recursion.cpp

@@ -0,0 +1,25 @@
+
+
+
+#include<iostream>
+using namespace std;
+
+int knapsack(int value[],int wt[],int n,int w)
+{
+    if(n==0 || w==0){
+        return 0;
+    }
+    if(wt[n-1]>w){
+        return knapsack(value,wt,n-1,w);
+    }
+    return max(knapsack(value,wt,n-1,w-wt[n-1])+value[n-1], knapsack(value,wt,n-1,w));
+}
+
+int main()
+{
+    int value[]={100,50,150};
+    int wt[]={10,20,30};
+    int w = 50;
+    cout<<knapsack(value,wt,3,w);
+    return 0;
+}

find m in stack.cpp

@@ -0,0 +1,118 @@
+
+/* C++ Program to implement a stack
+that supports findMiddle() and
+deleteMiddle in O(1) time */
+#include <bits/stdc++.h>
+using namespace std;
+
+class myStack {
+    struct Node {
+        int num;
+        Node* next;
+        Node* prev;
+
+        Node(int num) { this->num = num; }
+    };
+
+    // Members of stack
+    Node* head = NULL;
+    Node* mid = NULL;
+    int size = 0;
+
+public:
+    void push(int data)
+    {
+        Node* temp = new Node(data);
+        if (size == 0) {
+            head = temp;
+            mid = temp;
+            size++;
+            return;
+        }
+
+        head->next = temp;
+        temp->prev = head;
+
+        // update the pointers
+        head = head->next;
+        if (size % 2 == 1) {
+            mid = mid->next;
+        }
+        size++;
+    }
+
+    int pop()
+    {
+      int data=-1;
+        if (size != 0) {
+          data=head->num;
+            if (size == 1) {
+                head = NULL;
+                mid = NULL;
+            }
+            else {
+                head = head->prev;
+                head->next = NULL;
+                if (size % 2 == 0) {
+                    mid = mid->prev;
+                }
+            }
+            size--;
+        }
+      return data;
+    }
+
+    int findMiddle()
+    {
+        if (size == 0) {
+            return -1;
+        }
+        return mid->num;
+    }
+
+    void deleteMiddle()
+    {
+        if (size != 0) {
+            if (size == 1) {
+                head = NULL;
+                mid = NULL;
+            }
+            else if (size == 2) {
+                head = head->prev;
+                mid = mid->prev;
+                head->next = NULL;
+            }
+            else {
+                mid->next->prev = mid->prev;
+                mid->prev->next = mid->next;
+                if (size % 2 == 0) {
+                    mid = mid->prev;
+                }
+                else {
+                    mid = mid->next;
+                }
+            }
+            size--;
+        }
+    }
+};
+
+int main()
+{
+    myStack st;
+    st.push(11);
+    st.push(22);
+    st.push(33);
+    st.push(44);
+    st.push(55);
+    st.push(66);
+    st.push(77);
+    st.push(88);
+    st.push(99);
+    cout <<"Popped : "<< st.pop() << endl;
+    cout <<"Popped : "<< st.pop() << endl;
+    cout <<"Middle Element : "<< st.findMiddle() << endl;
+    st.deleteMiddle();
+    cout <<"New Middle Element : "<< st.findMiddle() << endl;
+    return 0;
+}