accumulate

问题 #include <iostream> #include <vector> #include <numeric> #include <iterator> using namespace std; int main() { int N; cin>>N; long long int x,sum=0; std::vector<long long int> v; for(int i=0;i<N;i++) { cin>>x; v.push_back(x); } /*vector<long long int>::iterator itr; itr = v.begin(); for(itr=v.begin();itr<v.end();itr++) sum += *itr;*/ sum = accumulate(v.begin(),v.end(),0); cout<<sum; return 0; } My program is returning abstract value using accumulate, but if I use the for loop, the answer is

问题 #include <iostream> #include <vector> #include <numeric> #include <iterator> using namespace std; int main() { int N; cin>>N; long long int x,sum=0; std::vector<long long int> v; for(int i=0;i<N;i++) { cin>>x; v.push_back(x); } /*vector<long long int>::iterator itr; itr = v.begin(); for(itr=v.begin();itr<v.end();itr++) sum += *itr;*/ sum = accumulate(v.begin(),v.end(),0); cout<<sum; return 0; } My program is returning abstract value using accumulate, but if I use the for loop, the answer is

问题 #include <iostream> #include <vector> #include <numeric> #include <iterator> using namespace std; int main() { int N; cin>>N; long long int x,sum=0; std::vector<long long int> v; for(int i=0;i<N;i++) { cin>>x; v.push_back(x); } /*vector<long long int>::iterator itr; itr = v.begin(); for(itr=v.begin();itr<v.end();itr++) sum += *itr;*/ sum = accumulate(v.begin(),v.end(),0); cout<<sum; return 0; } My program is returning abstract value using accumulate, but if I use the for loop, the answer is

问题 Assume I have vector of strings and I want concatenate them via std::accumulate. If I use the following code: std::vector<std::string> foo{"foo","bar"}; string res=""; res=std::accumulate(foo.begin(),foo.end(),res, [](string &rs,string &arg){ return rs+arg; }); I can be pretty sure there will be temporary object construction. In this answer they say that the effect of std::accumulate is specified this way: Computes its result by initializing the accumulator acc with the initial value init and

问题 Assume I have vector of strings and I want concatenate them via std::accumulate. If I use the following code: std::vector<std::string> foo{"foo","bar"}; string res=""; res=std::accumulate(foo.begin(),foo.end(),res, [](string &rs,string &arg){ return rs+arg; }); I can be pretty sure there will be temporary object construction. In this answer they say that the effect of std::accumulate is specified this way: Computes its result by initializing the accumulator acc with the initial value init and

问题 In C++20, many (most?) C++-standard-library algorithms have been made constexpr . Yet - std::accumulate has not. It seems like it could have been: template<class InputIt, class T> constexpr T accumulate(InputIt first, InputIt last, T init) { for (; first != last; ++first) { init = std::move(init) + *first; } return init; } So - is there a reason it wasn't constexpr 'ed as well? Note: This question was motivated by my answer to this question on compile-time accumulation. 回答1: P1645R1 was

问题 I have a dataset of patients getting treatments in various hospitals (in-patient only) wherein some analysis has revealed several inconsistencies. One of these was that - software was allowing patients to get admission without closure of their previously open case_id . In order to understand it better, let us consider the sample dataset sample data dput(df) df <- structure(list(case_id = 1:22, patient_id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 3L, 3L, 3L, 4L, 4L, 5L, 5L, 6L, 7L, 8L,

来源： https://stackoverflow.com/questions/48865040/pythonic-reduce-with-accumlation-and-arbitrary-lambda-function

来源： https://stackoverflow.com/questions/48865040/pythonic-reduce-with-accumlation-and-arbitrary-lambda-function

问题 I need to sum up some vectors; that is, I want to sum the nth elements of every vector and make a new vector with the result. (I've already ensured that the input vectors are all the same size.) I'd like to do this with the excellent range-v3 library. I've tried this: // This file is a "Hello, world!" in C++ language by GCC for wandbox. #include <iostream> #include <cstdlib> #include <vector> #include <cmath> #include <map> #include <range/v3/all.hpp> int main() { std::cout << "Hello, Wandbox