added important queue algos

Data Structures/Queue/QueueReversal.java

@@ -0,0 +1,23 @@
+class GfG{
+    public Queue<Integer> rev(Queue<Integer> q){
+        //add code here.
+        //revHelperRecursive(q);
+        revHelperIterative(q);
+        return q;
+    }
+    private void revHelperIterative(Queue<Integer> q){
+        Stack<Integer> s=new Stack<Integer>();
+        while(!q.isEmpty()){
+            s.push(q.poll());
+        }
+        while(!s.empty()){
+            q.offer(s.pop());
+        }
+    }
+    private void revHelperRecursive(Queue<Integer> q){
+        if(q.isEmpty())return;
+        int temp=q.poll();
+        revHelperRecursive(q);
+        q.offer(temp);
+    }
+}

Data Structures/Queue/TruckTour/TruckTour.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+class PetrolPump
+{
+    public int petrolGiven;
+    public int distanceToNext;
+    public PetrolPump(int PetrolGiven,int DistanceToNext)
+    {
+        this.petrolGiven = PetrolGiven;
+        this.distanceToNext = DistanceToNext;
+    }
+}
+class Solution {
+    static void Main(String[] args) {
+        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
+        int n = int.Parse(Console.ReadLine());
+        PetrolPump[] q = new PetrolPump[n];
+        for (int i = 0; i < n; i++)
+        {
+            int[] info = Array.ConvertAll(Console.ReadLine().Split(' '),int.Parse);
+            q[i]=new PetrolPump(info[0],info[1]);
+        }
+        TruckTour(q,n);
+    }
+    private static void TruckTour(PetrolPump[] q, int n)
+    {
+        int start = 0,end=1;
+        int curr_petrol= q[start].petrolGiven- q[start].distanceToNext;
+        while(curr_petrol<0 || start != end)
+        {
+            while(curr_petrol<0 && start != end)
+            {
+                curr_petrol -= (q[start].petrolGiven - q[start].distanceToNext);
+                start = (start + 1) % n;
+                if (start == 0)
+                {
+                    Console.WriteLine("Not Possible");
+                    return;
+                }
+            }
+            curr_petrol += q[end].petrolGiven - q[end].distanceToNext;
+            end = (end + 1) % n;
+        }
+        Console.WriteLine(start);
+    }
+}