added algo for stack using 2 queues in cpp

Author: ooreally

Array Stacking Algorithm/C++/stackusing2qs.cpp

@@ -0,0 +1,94 @@
+#include<iostream>
+using namespace std;
+
+struct qu1// queue1 declaration {
+   qu1 *n1;
+   int d1;
+}*f1 = NULL, *r1 = NULL, *q1 = NULL, *p1 = NULL, *np1 = NULL;
+
+struct qu2// queue2 declaration {
+   qu2 *n2;
+   int d2;
+}*f2 = NULL, *r2 = NULL, *q2 = NULL, *p2 = NULL, *np2 = NULL;
+
+void enqueue1(int a) {
+   np1 = new qu1;
+   np1->d1 = a;
+   np1->n1 = NULL;
+   if (f1 == NULL) {
+      r1 = np1;
+      r1->n1 = NULL;
+      f1 = r1;
+   } else {
+      r1->n1 = np1;
+      r1 = np1;
+      r1->n1 = NULL;
+   }
+}
+
+int dequeue1() {
+   int a;
+   if (f1 == NULL) {
+      cout<<"no elements present in queue\n";
+   } else {
+      q1 = f1;
+      f1 = f1->n1;
+      a = q1->d1;
+      delete(q1);
+      return a;
+   }
+}
+
+void enqueue2(int a) {
+   np2 = new qu2;
+   np2->d2 = a;
+   np2->n2 = NULL;
+   if (f2 == NULL) {
+      r2 = np2;
+      r2->n2 = NULL;
+      f2 = r2;
+   } else {
+      r2->n2 = np2;
+      r2 = np2;
+      r2->n2 = NULL;
+   }
+}
+
+int dequeue2() {
+   int a;
+   if (f2 == NULL) {
+      cout<<"no elements present in queue\n";
+   } else {
+      q2 = f2;
+      f2 = f2->n2;
+      a = q2->d2;
+      delete(q2);
+      return a;
+   }
+}
+
+int main() {
+   int n, a, i = 0;
+   cout<<"Enter the number of elements to be entered into stack\n";
+   cin>>n;
+   while (i < n) {
+      cout<<"enter the element to be entered\n";
+      cin>>a;
+      enqueue1(a);
+      i++;
+   }
+   cout<<"\n\nElements popped\n\n";
+   while (f1 != NULL || f2 != NULL)// if both queues are not null {
+      if (f2 == NULL)// if queue 2 is null {
+         while (f1->n1 != NULL) {
+            enqueue2(dequeue1());
+         }
+         cout<<dequeue1()<<endl;
+      } else if (f1 == NULL)//if queue 1 is null {
+         while (f2->n2 != NULL) {
+            enqueue1(dequeue2());
+         }
+         cout<<dequeue2()<<endl;
+      }
+   }
+}