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问题 I know that multi-thread read access to an std::se t or std::map is safe, but what about doing copy operations like std::map<int, int> node_info; int node = 2; int node_value; if (node_info.find(node) != node_info.end()) current_val = map_of_val[node].front(); I lock the maps when I am using .push() or .pop() for synchronized access, but my code is behaving erratically and I would like to know if know if this is causing instability. 回答1: Locking on push() and pop() isn't enough. If one thread

问题 Basically, I want to save a set of pointers, which should be sorted by my customized compare function, but the uniqueness should still be determined by the pointer itself. However: #include <iostream> #include <string> #include <set> #include <utility> #include <functional> using namespace std; // count, word typedef pair<int, string> WordFreq; struct WordFreqPointerCmp { bool operator()(const WordFreq* lhs, const WordFreq* rhs) const { return lhs->first > rhs->first; } }; int main() { set

问题 I want to get variable other class(jframe) but get method returns null.. But set method is running.. public class FrameGauges extends javax.swing.JFrame { Elm32x elma=null; private void jToggleButton1ActionPerformed(java.awt.event.ActionEvent evt) { FrameBaglanti a = new FrameBaglanti(); elma = a.GetElm(); System.out.println(elma); } } I added initialized case.. When I run getElm(), that returns null... What should i do ? public class FrameBaglanti extends javax.swing.JFrame { Elm32x elm;

问题 I wrote a c++ code as follows: #include<iostream> #include<string> #include<set> using namespace std; class data{ int i; float f; char c; public: data(); data(int i,float f,char c); }; data::data(int i,float f,char c){ this->i=i; this->f=f; this->c=c; }; class LessComparer{ bool operator<( const data& a1, const data& a2 ) const{ return( a1.i < a2.i || (!(a1.i > a2.i) && (a1.f < a2.f)) || (!(a1.i > a2.i) && !(a1.f > a2.f) && (a1.c < a2.c))); } }; int main(){ set<data,LessComparer> s; set<data

问题 I need a group of TVertex objects to have an access to their sortings by diffrent parameters (id and flow). To find the kth element in O(1) time and to update their properties in o(log2(N)) time. To do this I use TComparatorF and TComparatorI classes. They both have a pointer to TVertex and operators > and < TComparatorF compares flows TComparatorI compares ids TVertex() puts a pointer to itself to a comparator. And then puts the comparator to a set of comparators. But when I update

问题 I have a list like below L = [[1,2],[1,3],[1,4],[2,1],[2,5],[3,1],[3,2]] The output should be [[1,2],[1,3],[1,4],[2,5],[3,2]] Please note that the order for the pairs and the elements has to be preserved. In other words, I cannot sort the list because the elements order needs to be preserved for the pairs as well. For example, I need the last element [3,2] to be preserved. If i sort them and remove duplicates this will be changed to [2,3] which I do not want. Also when I say I need to remove

问题 EDIT I have a grayscale image which contains pixel values of 300 , which I assigned manually to pixels that hold a specific criterion. The case is that the other values in the image are 1 and 2 . So, I will have three values now: 1 , 2 , and 300 . In order to display the image in a meaningful way, we can use thresholding . So, this is as for the pixels with values 1 and 2 . For the pixels with the value 300 , how can I assign it some colour to be able to discriminate it from other parts of

问题 I am merely wanting to output the contents of a set (because I have to use this cursed and inflexible type), but every time I go to do it or loop through and print each element, I get the last one instead of the rest. Here's my entire code: def factorial(n): r = 1 for i in range(1, n + 1): r *= i return r def nCr(n, r): return factorial(n) / (factorial(r) * factorial(n - r)) def combinations(s, tokens): maxcombos = int(nCr(len(s), tokens)) for index in range(maxcombos): token_copy = tokens

问题 I hope I'll be clear.... In my code, I define a box which holds a set of elements ( bead ): vector<vector<vector<set<std::tr1::shared_ptr<bead> > > > > boxes; I am adding element to the box using: boxes[i][j][k].insert(aBead); For some reason I get a segmentation fault here. As far as I can tell, The segmentation fault does not occur because of illegal bead and i , j , k , are all smaller than the box's size and are not negative. In case you wonder bead is: class particle{ public: vec pos;

问题 I want to store a Swift Set in NSUserDefaults. Given that I can read a NSMutableSet value from UserDefaults using: UserDefaults.standard.mutableSetValue(forKey:) ... it seems like I should be able to write a NSMutableSet too. I tried converting my Set to NSMutableSet, but when I try to save it in UserDefaults it says: [User Defaults] Attempt to set a non-property-list object {( foo )} as an NSUserDefaults/CFPreferences value for key KEYNAME 回答1: mutableSetValue(forKey:) has an unfortunate