Simultaneously traversing of List by 2 Variables

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I am working on a code in which I am traversing a list, for example:

a = [1,2,3,4,5,6,7,8]

There are 8 elements(assuming that 'a' will always have even numbers) and I want to access 2 at a time, means the loop will execute 4 times. Every time the variable will increase by 2, like the odd and even numbers

b =1
for i range(len(a)/2):
    print(a[2*b-1],a[2*b])
    b += 1

the output will be an error because list index starts from 0 and ends on 3 and the list index will be out of range. this will not print 1 and 8 what do I have to do?

For the most recent version of your code the minimal fix (most close to the original solution)

b = 0
for i in range(len(a)/2):
    print(a[2*b], a[2*b+1])
    b += 1

A better solution is

for i in range(len(a)/2):
     print(a[2*i], a[2*i+1])

To handle even length use range((len(a) + 1) /2)

How To Iterate Over Two (or More) Lists at the Same Time, Taking the length of one list and using a placeholder index variable, often named i , you manually access each position in the lists. a = [1,2,3,4  Although you are expecting both sizes to be same, just to be on safer side get the sizes for both of them and make sure they are equal. Let that size value be count.Then use generic for loop, iterate till count and acess the values as array indexes.

I think changing 2*i-1 to 2*i+1. That's a simple question.

Python Iterate over multiple lists simultaneously, Python Iterate over multiple lists simultaneously. Iterating over single lists, refers to using for loops for iteration over a single element of a single list at a particular  Node ptr; // Help variable used to "visit" a Node object ptr = head; // Start with a visit to the first node while ( ptr has not reach the end of the list) {// You would normally write statements here to // read/update variables inside the Node object // that ptr is currenly "visiting" ptr = ptr.next; // ptr will point to the next node !

You can iterate two-by-two without having to worry about indexing by creating a single iterator with iter and then zip it with itself.

This is similar to the grouper function from itertools' recipes and has the advantage of being able to treat any iterarable, including non-indexed ones such as generators.

def iter_two_by_two(it):
    it = iter(it)
    yield from zip(it, it)

a = [1, 2, 3, 4, 5, 6, 7, 8]

for pair in iter_two_by_two(a):
    print(pair)
Output
(1, 2)
(3, 4)
(5, 6)
(7, 8)

Data Structures and Algorithms in Java, We can evaluate such equivalence by simultaneously traversing two lists, it to a SinglyLinkedList, so that we may access its instance variables size and head. Use your language's "for each" loop if it has one, otherwise iterate through the collection in order with some other loop. For this example, loop over the arrays: (a,b,c) (A,B,C) (1,2,3) to produce the output: If possible, also describe what happens when the arrays are of different lengths. Loops/Downward for. Loops/For with a specified step.

Looping Through Multiple Lists - Python Cookbook [Book], Looping Through Multiple Lists Credit: Andy McKay Problem You need to loop through every item of multiple lists. Solution There are basically three approaches  If you don't want to wait for .NET 4.0, you could implement your own Zip method. The following works with .NET 2.0. You can adjust the implementation depending on how you want to handle the case where the two enumerations (or lists) have different lengths; this one continues to the end of the longer enumeration,

Loop over multiple arrays simultaneously, Loop over multiple arrays (or lists or tuples or whatever they're called in your way to loop over all of them is to simply use an index variable. C# - List<T> You have already learned about ArrayList in the previous section. An ArrayList resizes automatically as it grows. The List<T> collection is the same as an ArrayList except that List<T> is a generic collection whereas ArrayList is a non-generic collection.

Understanding Control Flow: Concurrent Programming Using μC++, 2.14 List/iterator doubly linked list, the cost for these operations can be very expensive; iterator and reverse_iterator, are used to simultaneously traverse the list. Because the iterator is an object, there can be multiple iterators instantiated, variables between calls to the traversal operators, ++/--, such as the list being  Step by step descriptive logic to traverse a linked list. Create a temporary variable for traversing. Repeat below step till temp != NULL. temp->data contains the current node data. Once done, move to next node using temp = temp->next;. Go back to 2nd step.

Comments
  • yes actually the i is wrong there i have to place a different variable can you it now
  • the new version makes no sense at all. Well you can add increment of b, b += 1 but it is simpler with i?
  • do not forget missing in keyword in the loop, decrement index even one more,print(a[2*b-2],a[2*b - 1]) and make clear in the question what was original question and which result worked for you. That will looks stupid but will work
  • yes, this works correctly, but now what is the use of 'b' here, in the upper solution?
  • then can you please add the solution