没有合适的构造函数存在 - 矢量图

Posted 2023-02-25

【中文标题】没有合适的构造函数存在 - 矢量图

【英文标题】：No Suitable Constructor Exists - Vector

【发布时间】：2021-08-04 09:31:08

【问题描述】：

我今天为自己开始了一个简单的编码项目，但我无法弄清楚这个错误或如何解决它。我得到的错误发生在我的do 循环中。更具体地说，它发生在每个将Nums 作为参数传递的函数调用中。错误状态no suitable constructor exists to convert from to "std::vector<int, std::allocator<int>> [10]" to "std::vector<int, std::allocator<int>>"

对此的任何帮助将不胜感激！蒂亚！

//This program checks to see if a multiplied vector value is odd or even
//CheckOddEven.cpp

#include <iostream>
#include <vector>
#include <numeric>

using namespace std;

int setSize(int size, vector <int> Nums) //Sets vector size to user defined size

        //Prompt user to enter an integer to establish array size
        cout << "How many integers would you like to multiply?: ";

        //Store user input to size
        cin >> size;

        //Resize vector to user size
        Nums.resize(size);

        return size;


vector <int> setNum(int size, int x, vector <int> Nums) //Sets values in each index

        //Insertion loop to Nums vector
        for (int i = 0; i < size; i++)
        
                cout << "Enter integer #" << i + 1 << ": ";
                cin >> x;
                Nums.push_back(x); //Assigns value into vector
        

        return Nums;


int doMath(vector <int> Nums, int result)

        //Loop through Nums vector and multiply all values
        accumulate(Nums.begin(), Nums.end(), result, multiplies<int>());

        return result;


string oddEven(int result, string msg) //Check if int is even by seeing if there is a remainder

        //If no remainder exists then positive
        if (result % 2 == 0)
                
                        msg += "positive.";
                
                
        //If remainder exists then negative
        else
        
                msg += "negative.";
        

        return msg;


void Display(int result, string msg)

        cout << "The product of your integers is " << result << endl;
        cout << msg;


char checkCont(char cont)

        //Asks user if they want to check another integer
        cout << "Would you like to check another? (y/n)" << endl;

        //Assigns input as char into cont
        cin >> cont;

        //Displays exit message and ends do-while
        if (cont == 'n' || cont == 'N')
        
                cout << "Thank you for using the Odd-Even Checker!" << endl;
                cout << "Have a great day!" << endl;
        

        return 'z';


int main()

        int size; //User defined vector size
        string msg = "The number you calculated is ";
        char cont = ' '; //Char value for checking another vector
        vector <int> Nums[10]; //Create int vector with predetermined size..can be changed with resize
        int x; //User numbers
        int result;

        cout << "Welcome to the Odd-Even Checker!" << endl;
        cout << "This program multiplies a given amount of numbers, then checks to see if the answer is even or odd." << endl;

        do //Requires to run at least once
        
                setSize(size, Nums);
                setNum(size, x, Nums);
                doMath(Nums, result);
                oddEven(result, msg);
                Display(result, msg);
                checkCont(cont);
         while (cont == 'y' || cont == 'Y'); //end do-while

        return 0;

【问题讨论】：

这不是 C。不要滥用标签。

【参考方案1】：

你声明了一个向量数组

vector <int> Nums[10];

但是将此数组传递给需要向量类型的标量对象的函数

int setSize(int size, vector <int> Nums);

//...

setSize(size, Nums);

也许你指的是一个包含 10 个元素的向量而不是数组

vector <int> Nums(10);

或者只是一个空向量

vector <int> Nums;

似乎还有一个问题是您没有通过引用传递向量。例如，函数setSize 处理传递的向量的副本。

因此函数内的这条语句

Nums.resize(size);

没有意义。

将函数中需要向量函数参数的类型更改为引用类型，如

int setSize(int size, vector <int> &Nums);
                                  ^^^^^^

注意参数size的值没有在函数内部使用，所以参数size没有意义。

这个函数也没有意义

int doMath(vector <int> Nums, int result)

        //Loop through Nums vector and multiply all values
        accumulate(Nums.begin(), Nums.end(), result, multiplies<int>());

        return result;

调用算法std::accumulate后变量结果没有改变。

您还传递了一个未初始化的变量结果

int result;

你至少应该写

long long int doMath( const std::vector<int> &Nums )

        //Loop through Nums vector and multiply all values
    long long result = std::accumulate(Nums.cbegin(), Nums.cend(), 1ll, std::multiplies<long long>());

    return result;

您应该将您的程序拆分成小的子程序并分别测试每个使用的功能，因为您似乎不明白自己在做什么。之后，您可以将所有子程序组合在一个程序中。

例如要测试函数setSize，你可以写一个像这样的简单程序

#include <iostream>
#include <vector>

std::vector<int>::size_type setSize( std::vector<int> &Nums )

    //Prompt user to enter an integer to establish array size
    std::cout << "How many integers would you like to multiply?: ";

    //Store user input to size
    std::vector<int>::size_type size = 0;
    std::cin >> size;

    //Resize vector to user size
    Nums.resize( size );

    return size;


int main() 

    std::vector<int> Nums;
    
    auto size = setSize( Nums );
    
    if ( size == Nums.size() )
    
        std::cout << "The function works correctly.\n";
    
    else
    
        std::cout << "Something is wrong with the function!\n";
    
    
    return 0;

在您确定该功能按预期工作后，您可以将其添加到主程序中。