通过构造函数为向量预先分配C++内存失败开发者社区

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const int elemNumber = 100000000;
    //std::vector<int>* intVector = new std::vector<int>(elemNumber); // throws bad_alloc
    std::vector<int>* intVector = new std::vector<int>();
    intVector->reserve(elemNumber); //OK
    std::chrono::time_point<std::chrono::system_clock> start, end;
    start = std::chrono::system_clock::now();
    for (int i = 0; i < elemNumber; ++i)
        intVector->push_back(i);
    end = std::chrono::system_clock::now();
    std::chrono::duration<double> elapsed_seconds = end - start;
    std::cout << "Time interval: " << elapsed_seconds.count() << endl;
    delete intVector;
    cout << "Done" << endl;
catch (bad_alloc exc)
    cout << exc.what() << endl;
}

#include <iostream>
#include <chrono>
#include <vector>
int main()
    const int elemNumber = 5;
        std::vector<int> intVector(elemNumber); // throws bad_alloc
        std::chrono::time_point<std::chrono::system_clock> start, end;
        start = std::chrono::system_clock::now();
        for (int i = 0; i < elemNumber; ++i)
            //intVector[i] = i;
            intVector.push_back(i);
        //prints the vector
        for (auto& i : intVector)
            std::cout << i << std::endl;
        end = std::chrono::system_clock::now();
        std::chrono::duration<double> elapsed_seconds = end - start;
        std::cout << "Time interval: " << elapsed_seconds.count() << std::endl;
        std::cout << "Done" << std::endl;
    catch (std::bad_alloc exc)
        std::cout << exc.what() << std::endl;
    std::cin.get();

问 通过构造函数为向量预先分配C++内存失败 EN

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