Merge pull request bamsarts#1 from rishav4336/rishav4336-patch-1

Add files via upload

queue/prefix_evaluation.cpp

@@ -0,0 +1,97 @@
+#include<iostream>
+#include<cstring>
+using namespace std;
+union u
+{
+	int i;
+	char ch;
+};
+struct queue
+{
+	int tag;
+	int f;
+	int r;
+	union u elements[50];
+	int size;
+};
+void enqueue(queue &q,char x)
+{
+	int tag;
+	if(q.f==(q.r+1)%q.size)
+		cout<<"queue is full";
+	else
+	{
+		if(q.r==-1)
+			q.f=0;
+		q.r=(q.r+1)%q.size;
+		cout<<"enter tag char =0,int=1"<<endl;
+		cin>>q.tag;
+		if(q.tag==0)
+			q.elements[q.r].ch=x;
+		else
+			q.elements[q.r].i=x-'0';		
+		}	
+}
+u dequeue(queue &q)
+{
+	u t;
+	if(q.f==-1)
+		cout<<"queue is empty";
+	else
+	{
+		t=q.elements[q.f];
+		if(q.f==q.r)
+		{
+			q.f=-1;
+			q.r=-1;
+		}
+		else
+			q.f=(q.f+1)%q.size;
+		}	
+		return t;
+}
+int eval(int b,int a,char c)
+{
+	switch(c)
+		{
+			case'+':
+					return a+b;
+					break;
+				case'-':
+					return a-b;
+					break;
+				case'*':
+					return a*b;
+					break;
+				case'/':
+					return a/b;
+					break;
+
+		}
+}
+
+int main()
+{
+	struct queue q;
+	q.f=-1;
+	q.r=-1;
+	q.size=50;
+	string s;
+	u a,b,c;
+	cout<<"enter prefix list"<<endl;
+	getline(cin,s);
+	a=dequeue(q);
+	while(q.f!=q.r)
+	{
+		if(!isdigit(a))
+			dequeue(q);
+		else
+		{
+			enqueue(q,a);
+			a=b;
+			b=c;
+				c=dequeue(q);
+			}	
+	}
+	cout<<dequeue(q)<<endl;
+}