You can do this by building a set of integers and adding larger seen in the set, and holding the minimum not seen in as a counter. Once there is a number that is equal to the latter, go through the set removing elements until there is a missing integer. Please see below for implementation. … Read more
Something along the lines of std::vector<std::pair<int, int>> find_nonmatching_values(const std::unordered_multimap<int, int> & thing, int key, int value) { std::vector<std::pair<int, int>> ret; auto range = thing.equal_range(key); std::copy_if(range.first, range.second, std::back_inserter(ret), [value](const std::pair<const int, int> &p) { return p.second != value; }); return ret; } Demo. Templatizing this code is left as an exercise for the reader. solved Search … Read more
everything seems to be ok with this code. #include <vector> #include <array> int main() { std::vector< std::array<int,8> > output; output.resize(8); return 0; } Ideone test example Have you added the #include <array> line? 5 solved std::array as element type of another standard container? [closed]
Every #include directive including something from the C++ standard library “loads” the entities into the std namespace (or some other namespace like this). The namespace helps preventing global namespace pollution – by keeping everything in a seperate namespace, identifier collisions are rendered impossible. In the <vector> file, then there is something like namespace std { … Read more
Just use std::inner_product: live demo #include <algorithm> #include <iostream> #include <iterator> #include <ostream> #include <numeric> #include <cstdlib> #include <vector> using namespace std; int main() { vector<int> v1,v2; generate_n( back_inserter(v1), 256, rand ); generate_n( back_inserter(v2), v1.size(), rand ); cout << inner_product( v1.begin(), v1.end(), v2.begin(), 0 ) << endl; } Yes, that’s a good solution. But I … Read more
You can use a std::vector without initializing its size and it supports random access. To add to an empty std::vector use push_back std::vector<MyType> vec; vec.push_back(MyType(10, ‘a’, “Hi”)); vec.push_back(MyType(20, ‘b’, “Hello”)); vec.push_back(MyType(30, ‘c’, “Bye”)); MyType t = vec[1];//20,’b’, “Hello”… Edit: This answer is for the question that was originally asked. 3 solved Why doesn’t this code … Read more
All three options to check for empty container are more or less equivalent. Using empty() shows (as denoted in the comments already) most obviously your intention and as a little bonus, it is even the shortest one to write (that’s for the lazy ones like me…). How it is implemented? Vendor specific, probably inlined. Option … Read more
The find member function of std::map specializations returns a past-the-end iterator if the key does not exist. So you need to compare to the container’s end(): auto f = cnt.find(“asdasd”); if (f != cnt.end()) { std::cout << f->second; } solved Program crashes on trying to access the key that does not exist in map [duplicate]
Function signature is void push_back (const value_type& val); and the value passed is copied in your list. So you can consider this a “pass-by-value” (in a operational way). In C++11 you have also void push_back (value_type&& val); that is a possibilities of move your value into your list. solved C++ STL list’s Push_back takes argument … Read more
I don’t understand why you are using std::vector. You could calculate the sum without using the vector: int k=0,sum=0; for(int i=0;i<s.length();i++) { k = s[i]-‘0′; sum += k; } Note: if you are a little paranoid of the sum value fitting into an integer, you can use an unsigned integer since digits can’t be negative. … Read more
You can do it like that for (int i = 0; i < present.size(); ++i) cout << present[i]->id << ” “; or in C++11 for (auto p : present) cout << p->id << ” “; I hope it helps solved Displaying the elements of a vector of structure [closed]
You need to go from l to m when filling vector L: void merge(vector<int>& a, int l, int m, int r) { vector<int> L; vector<int> R; for (int i = l; i <= m; i++) L.push_back(a[i]); … } Otherwise L contains additional elements outside the range of interest. Then, index k steps off the end … Read more
The original poster failed to actually post the code that was causing the problem. He has since edited my post with the correct code that demonstrates the problem. The code that demonstrates the problem follows: template <class R, typename B=int> class AVectorContainer { public: AVectorContainer() {} typedef R* ptr_Type; typedef const B & const_ref_Type; typedef … Read more
This uses std::for_each() because you asked for STL: #include <string.h> #include <string> #include <algorithm> void inlineConvertPackFilename(std::string& name) { std::for_each(name.begin(), name.end(), [](auto& c) { if (c == ‘\\’) { c=”https://stackoverflow.com/”; } else { c = tolower(c); } }); } int main() { static std::string filename(“C:\\FOO\\bar\\Baz.txt”); inlineConvertPackFilename(filename); return 0; } But that’s really unnecessary as you can … Read more
I can only assume that a side effect of calculateSomeValue() is changing a which invalidates all iterators. Since the order of evaluation of arguments in a.insert(a.begin(), calculateSomeValue()); is unspecified it could be that a.begin() is evaluated before calculateSomeValue() invalidates all iterators to a. Which is undefined behaviour. solved discussion about the scenarios that the insertion … Read more