deque

问题 I am building my first ever program in C++ over and over again. The program is intended to create a picture, a gradient - with parameters of height h , width l , in pixels, and 4 parameters of density Da, Db, Dc, Dd . This gradient is produced by '1 bit' pixels: they are black or white - and by the simplest error-diffusion algorithm (so-called "naive" sometimes), >> push the error on the next pixel of the line. After having performed an optimization ( deque instead of vector allows bigger

问题 I am trying to store iterators of a deque in a vector and want to preserve them inside the vector even when I have erased or inserted some elements from or into the deque. Is this possible? I have the following code: typedef struct { int id; int seedId; double similarity; } NODE_SEED_SIM; typedef std::deque<NODE_SEED_SIM> NodesQueue; typedef std::deque<NODE_SEED_SIM>::iterator ITRTR; typedef std::vector<const ITRTR> PointerVec; void growSegments (CSG_PointCloud *pResult, IntMatrix *WdIndices,

问题 I'm trying to reduce the processing time of reading a database with roughly 100,000 entries, but I need them to be formatted a specific way, in an attempt to do this, I tried to use python's multiprocessing.map function which works perfectly except that I can't seem to get any form of queue reference to work across them. I've been using information from Filling a queue and managing multiprocessing in python to guide me for using queues across multiple processes, and Using a global variable

问题 I have to refactor old code that looks like this (I am not a very proficient C++ coder) std::set<SomeObject>::iterator it = setobject.begin(); do { it->setProperty1ToNextValue(); it->getProperty2(); it->getProperty3(); it++ } while (it != setobject.end()); Basically I want to iterate through the elements of the set and get and set/update some of their properties. I cant use the original set since I run in the problems described in this thread the object has type qualifiers that are not

问题 I have a text document that I would like to repeatedly remove the first line of text from every 30 seconds or so. I have already written (or more accurately copied) the code for the python resettable timer object that allows a function to be called every 30 seconds in a non blocking way if not asked to reset or cancel. Resettable timer in python repeats until cancelled (If someone could check the way I implemented the repeat in that is ok, because my python sometimes crashes while running

问题 The following piece of code attempts to create a map that shows the minimum number of moves it would take to get from each square on that map to the specified location. The function as a whole is largely irrelevant to the problem, but I thought I should provide my problem in context. I've also imported deque from collections. The strange part comes in at line 7. I get TypeError: 'int' object not iterable. But the statement "distance_from_loc, f_loc = squares_to_check.popleft()" shouldn't be

问题 Why this code works fine: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; cell.textLabel.text = [NSString stringWithFormat:@"cell%i%i", indexPath.section, indexPath.row];

问题 This question already has answers here : How are deques in Python implemented, and when are they worse than lists? (5 answers) Closed 3 years ago . I am wondering about the time complexity of the get operation of deque in Python. I know that it is implemented as a doubly link in Python. Does that mean that its time complexity is O(n)? 回答1: deque are implemented a little smarter than just doubly-linked lists. They're a doubly-linked list of blocks of Python objects, where the left and right

问题 I always thought that in C++ standard template library (STL), a double-ended queue (deque) is a size-variable array (like a vector) with circular boundary conditions, meaning there's a head pointer i and a tail pointer j both pointing to some position of an array a[0..L-1] . A push_front is i-- , a push_back is j++ , a pop_front is i++ , and a pop_back is j-- . When either pointer i or j reaches L or -1 , it reappears on the other end of the array ( 0 and L-1 respectively). If the array size

问题 I was going over this post and it states that deque provides efficent insetion at the top and bottom.However this post here states that time complexity of deque other than the back is O(n).I would think that if a deque has efficent top and bottom insertion it would have O(1) while a vector should have O(1) at bottom insertion only. I would appreciate it if someone could clarify this 回答1: The cppreference entry for std::deque gives the following complexity: The complexity (efficiency) of