iteration

问题 My task is to generates all possible combinations of that rows without the hidden # square. The input is XOXX#OO#XO and here is the example of what the output should be: XOXXOOOOXO XOXXOOOXXO XOXXXOOOXO XOXXXOOXXO I am only allowed to solve this solution iteratively and I am not sure how to fix this and have been working on this code for a week now.. any help would be much appreciated! Here is my code: import java.lang.Math; public class help { public static void main(String[] args) { String

问题 I'm new to C# and looking at arrays. Given: int[][] myJagArray = new int[5][]; Why does the following print the types of j (System.Int32[]), and not each j's contents? foreach (int[] j in myJagArray) { Console.WriteLine("j : {0}",j); } 回答1: Because Array.ToString() does not return the contents of the array, it returns the type name, and Console.WriteLine implicitly calls ToString() on each object you send it as a parameter. This has no regard to the fact that the array is part of a multi

问题 I'm new to C# and looking at arrays. Given: int[][] myJagArray = new int[5][]; Why does the following print the types of j (System.Int32[]), and not each j's contents? foreach (int[] j in myJagArray) { Console.WriteLine("j : {0}",j); } 回答1: Because Array.ToString() does not return the contents of the array, it returns the type name, and Console.WriteLine implicitly calls ToString() on each object you send it as a parameter. This has no regard to the fact that the array is part of a multi

问题 I have 2 text files and I want to iterate over both of them simultaneously. i.e: File1: x1 y1 z1 A,53,45,23 B,65,45,32 File2: x2 y2 z2 A,0.6,0.9,0.4 B,8.6,1.0,2.3 and I want use values from both files simultaneously: e.g: c1 = x1*x2 + y1*y2 + z1*z2 #for first line c2 = x1*x2 + y1*y2 + z1*z2 #for second line How can one do that using Python? 回答1: You need to treat both files as iterators and zip them. Izip will allow you to read the files in a lazy way: from itertools import izip fa=open(

问题 I have got an array from which some items are going to be removed; but some loops are still running on them, so I want to simply skip the places where I remove my objects I know that the syntax for(i in array) should do this because it iterates on the index, but how should I remove my items then ? Because when i do array[4] = null, my for just doesn't care and goes on trying to use the value at 4. I also tried to check if !null but without success... thank you 回答1: If you want to remove an

问题 I have a time series data frame in R that has a column, V1, which consists of integers with a few NAs interspersed throughout. I want to iterate over this column and subtract V1 from itself one time step previously. However, I want to ignore the NA values in V1 and use the last non-NA value in the subtraction. If the current value of V1 is NA, then the difference should return NA. See below for an example V1 <- c(1, 3, 4, NA, NA, 6, 9, NA, 10) time <- 1:length(V1) dat <- data.frame(time =

问题 In the code I have gotten from my previous issue: issue I could use iterations whilst modifying the a value of multiplication. I want to use the .prod function but with iterations of multiplication, division and addition. The calculations will go as follows, for the first calculation 10 + 10 *50/100 = 15 with the equation (Starting_val + Starting_val * Random_numb/100) . The first element in Random_numb is 50 and Starting_val is updated to the value of 15. So for the second calculations it

问题 I'm trying to get the Cartesian product of multiple arrays but the arrays are pretty large and I am trying to optimize memory usage. I have tried implementing a generator by using the below code but it just returns that there is a generator at a certain location. import itertools x = [[1,2],[3,4]] def iter_tools(*array): yield list(itertools.product(*array)) print(iter_tools(*x)) When I try the same code but with return instead of yield it works fine. How could I get the cartesian product by

问题 map and filter are often interchangeable with list comprehensions, but reduce is not so easily swapped out as map and filter (and besides, in some cases I still prefer the functional syntax anyway). When you need to operate on the arguments themselves, though, I find myself going through syntactical gymnastics and eventually have to write entire functions to maintain readability. I'll use map to keep the illustration unit-test simple, but please keep in mind that real-life use-cases might be

问题 I have a list created with no more than 8 items in it, right now I loop over the item with a standard for loop "for item in list:" I am wondering if there is a way to check all of the elements at the exact same time? I have seen some posts about using zip to iterate over 2 lists at the same time which could help. If there is no way to iterate over a lists elements at the same time I would guess I need to split one single list into 4 separate lists and iterate 2 at the same time using zip and