Linked Questions

A recent talk about unordered_map in C++ made me realize that I should use unordered_map for most cases where I used map before, because of the efficiency of lookup ( amortized O(1) vs. O(log n) ). ...

I need to map primitive keys (int, maybe long) to struct values in a high-performance hash map data structure. My program will have a few hundred of these maps, and each map will generally have at ...

I’ve recently found out an odd thing. It seems that calculating Collatz sequence lengths with no caching at all is over 2 times faster than using std::unordered_map to cache all elements. Note I did ...

I am trying to create a map in C++ with bitset as a key. However the compiler generates the following error messages In file included from /usr/include/c++/4.6/string:50:0, from /usr/...

So far, I have been storing the array in a vector and then looping through the vector to find the matching element and then returning the index. Is there a faster way to do this in C++? The STL ...

I have a simple Observable class, implementing the observer pattern. This class maps a template type Event to registered observers. This is all fine, though instead of std::map I'd like to use std::...

Does MFC CMap have a good performance compared to std::unordered_map or std::map, I ask this question because I'm going to start a project in my company, and to accelerate the development I'm going a ...

I have to fill an array of 1000 objects by reading data from disk. However, not every objects exits. Once I declare an array, memory will be reserved for 1000 objects. As I read them one by one, I ...

I am iterating a map where I need to add elements on that map depending on a condition that an element is not found (it could be any other condition). My main problem is that with a big scale of ...

I have something stored in std::map, which maps string to vector. Its keys and values looks like key value "a"-----[1,2,3] "b"-----[8,100] "cde"----[7,10] For each thread, it needs to process ...

I have an efficiency critical application, where I need such an array-type data structure A. Its keys are 0, 1, 2,..., and its values are uint64_t distinct values. I need two constant operations: 1. ...

I've done some random tests but I couldn't come to a conclusion. If inserting 1000000 integers in to a map and an unordered_map, the time used by map is 3 times larger. If inserting 1000000 strings ...

I want to reduce copying to a minimum, especially for expensive types/classes. So I could define overloads like this: void SetParams(const std::map<int, std::string> &params) { mParams = ...

I want to get the information of how many times each number has repeated in array. I was doing something like this: for (int j = 0; j < n; j++){ cin >> x; arr[x]++; } ...