动态数组实现ElectionDistrict类报错：无匹配构造函数初始化ElectionDistrict[]

我正在编写一个管理选区选举结果的程序，需要存储选区名称等信息。运行时出现错误："No matching constructor for initialization of 'ElectionDistrict[]'"。要求不使用vector，仅通过动态数组解决该问题，同时程序需实现选区获胜方判定、结果打印及文件保存功能。

#include <iostream>
#include <fstream>
#include <algorithm>
#include <cstring>
#include <limits>

const int MAX_PARTIES = 10; /* Maximum number of parties*/

class ElectionDistrict {
private:
    char* name;
    int votersCount;
    int partiesCount;
    int* partyVotes;
    std::string* partyNames;

public:
    ElectionDistrict(const char* name, int voters, int parties) /* Constructor*/
            : votersCount(voters), partiesCount(parties) {
        this->name = new char[strlen(name) + 1];
        strcpy(this->name, name);

        partyVotes = new int[partiesCount];
        partyNames = new std::string[partiesCount];
    }

    ~ElectionDistrict() {  /*Destructor*/
        delete[] name;
        delete[] partyVotes;
        delete[] partyNames;
    }

    const char* getName() const { return name; }
    int getVotersCount() const { return votersCount; }
    int getPartiesCount() const { return partiesCount; }
    const int* getPartyVotes() const { return partyVotes; }
    const std::string* getPartyNames() const { return partyNames; }

    void setPartyVotes(int partyIndex, int votes) {
        partyVotes[partyIndex] = votes;
    }

    void setPartyName(int partyIndex, const std::string& partyName) {
        partyNames[partyIndex] = partyName;
    }

};

// Function to compare ElectionDistrict objects based on party votes
bool compareByPartyVotes(const ElectionDistrict& a, const ElectionDistrict& b) {
    return a.getPartyVotes()[0] > b.getPartyVotes()[0];
}

int main() {
    std::ofstream outFile("districts.txt");
    ElectionDistrict* districts;

    int numDistricts;

    std::cout << "Enter the number of districts: ";
    std::cin >> numDistricts;

    districts = new ElectionDistrict[numDistricts]; /* right here is the problem*/

    for (int i = 0; i < numDistricts; ++i) {
        char name[100];
        int voters, numParties;

        std::cout << "Enter the name of district " << i + 1 << ": ";
        std::cin >> name;

        std::cout << "Enter the number of voters in " << name << ": ";
        std::cin >> voters;

        std::cout << "Enter the number of parties in " << name << ": ";
        std::cin >> numParties;

        districts[i] = ElectionDistrict(name, voters, numParties);

        for (int j = 0; j < numParties; ++j) {
            std::string partyName;
            int votes;

            std::cout << "Enter the name of party " << j + 1 << " in " << name << ": ";
            std::cin >> partyName;

            std::cout << "Enter the number of votes for " << partyName << " in " << name << ": ";
            std::cin >> votes;

            districts[i].setPartyVotes(j, votes);
            districts[i].setPartyName(j, partyName);
        }
    }
    /*writing the information about each election district and its associated parties to output file (districts.txt)*/
    for (int i = 0; i < numDistricts; ++i) { 
        outFile << districts[i].getName() << " " << districts[i].getVotersCount() << " " << districts[i].getPartiesCount();
        for (int j = 0; j < districts[i].getPartiesCount(); ++j) {
            outFile << " " << districts[i].getPartyVotes()[j] << " " << districts[i].getPartyNames()[j];
        }
        outFile << std::endl;
    }
    outFile.close();

      // Rest of the code remains the same

    delete[] districts; // Release memory

    return 0;
}

错误原因 #

使用new ElectionDistrict[numDistricts]创建动态数组时，C++会为每个数组元素调用类的默认构造函数（无参构造），但当前ElectionDistrict类仅定义了带参数的构造函数，编译器不会自动生成默认构造函数，因此触发编译错误。

此外，类中包含指针成员（char* name、int* partyVotes等），默认的赋值运算符会执行浅拷贝，导致多个对象共享同一块内存，析构时重复释放内存引发崩溃，必须实现拷贝构造函数和赋值运算符重载。

修改步骤 #

1. 完善ElectionDistrict类 #

添加默认构造函数、拷贝构造函数、赋值运算符重载，同时新增获胜方判定和结果打印的成员函数：

class ElectionDistrict {
private:
    char* name;
    int votersCount;
    int partiesCount;
    int* partyVotes;
    std::string* partyNames;

public:
    // 默认构造函数
    ElectionDistrict() : name(nullptr), votersCount(0), partiesCount(0), partyVotes(nullptr), partyNames(nullptr) {}

    // 带参构造函数
    ElectionDistrict(const char* name, int voters, int parties) 
            : votersCount(voters), partiesCount(parties) {
        this->name = new char[strlen(name) + 1];
        strcpy(this->name, name);

        partyVotes = new int[partiesCount];
        partyNames = new std::string[partiesCount];
    }

    // 拷贝构造函数（深拷贝）
    ElectionDistrict(const ElectionDistrict& other) {
        votersCount = other.votersCount;
        partiesCount = other.partiesCount;

        // 拷贝名称
        if (other.name) {
            name = new char[strlen(other.name) + 1];
            strcpy(name, other.name);
        } else {
            name = nullptr;
        }

        // 拷贝政党票数
        if (other.partyVotes && partiesCount > 0) {
            partyVotes = new int[partiesCount];
            for (int i = 0; i < partiesCount; ++i) {
                partyVotes[i] = other.partyVotes[i];
            }
        } else {
            partyVotes = nullptr;
        }

        // 拷贝政党名称
        if (other.partyNames && partiesCount > 0) {
            partyNames = new std::string[partiesCount];
            for (int i = 0; i < partiesCount; ++i) {
                partyNames[i] = other.partyNames[i];
            }
        } else {
            partyNames = nullptr;
        }
    }

    // 赋值运算符重载（深拷贝）
    ElectionDistrict& operator=(const ElectionDistrict& other) {
        if (this == &other) return *this; // 防止自赋值

        // 释放当前对象的内存
        delete[] name;
        delete[] partyVotes;
        delete[] partyNames;

        // 拷贝成员变量
        votersCount = other.votersCount;
        partiesCount = other.partiesCount;

        // 拷贝名称
        if (other.name) {
            name = new char[strlen(other.name) + 1];
            strcpy(name, other.name);
        } else {
            name = nullptr;
        }

        // 拷贝政党票数
        if (other.partyVotes && partiesCount > 0) {
            partyVotes = new int[partiesCount];
            for (int i = 0; i < partiesCount; ++i) {
                partyVotes[i] = other.partyVotes[i];
            }
        } else {
            partyVotes = nullptr;
        }

        // 拷贝政党名称
        if (other.partyNames && partiesCount > 0) {
            partyNames = new std::string[partiesCount];
            for (int i = 0; i < partiesCount; ++i) {
                partyNames[i] = other.partyNames[i];
            }
        } else {
            partyNames = nullptr;
        }

        return *this;
    }

    ~ElectionDistrict() {  /*Destructor*/
        delete[] name;
        delete[] partyVotes;
        delete[] partyNames;
    }

    const char* getName() const { return name; }
    int getVotersCount() const { return votersCount; }
    int getPartiesCount() const { return partiesCount; }
    const int* getPartyVotes() const { return partyVotes; }
    const std::string* getPartyNames() const { return partyNames; }

    void setPartyVotes(int partyIndex, int votes) {
        if (partyIndex >= 0 && partyIndex < partiesCount) {
            partyVotes[partyIndex] = votes;
        }
    }

    void setPartyName(int partyIndex, const std::string& partyName) {
        if (partyIndex >= 0 && partyIndex < partiesCount) {
            partyNames[partyIndex] = partyName;
        }
    }

    // 判定获胜政党
    std::string getWinningParty() const {
        if (partiesCount == 0 || !partyVotes || !partyNames) {
            return "No parties recorded";
        }

        int maxVotes = -1;
        int winningIndex = 0;
        for (int i = 0; i < partiesCount; ++i) {
            if (partyVotes[i] > maxVotes) {
                maxVotes = partyVotes[i];
                winningIndex = i;
            }
        }
        return partyNames[winningIndex];
    }

    // 打印选区选举结果
    void printResults() const {
        std::cout << "选区名称: " << (name ? name : "未命名") << std::endl;
        std::cout << "选民总数: " << votersCount << std::endl;
        std::cout << "参选政党数: " << partiesCount << std::endl;
        std::cout << "各政党得票情况:" << std::endl;
        for (int i = 0; i < partiesCount; ++i) {
            std::cout << "  " << partyNames[i] << ": " << partyVotes[i] << " 票" << std::endl;
        }
        std::cout << "获胜政党: " << getWinningParty() << "\n" << std::endl;
    }
};

2. 修改main函数 #

在文件保存后添加结果打印逻辑：

int main() {
    std::ofstream outFile("districts.txt");
    ElectionDistrict* districts;

    int numDistricts;

    std::cout << "Enter the number of districts: ";
    std::cin >> numDistricts;

    districts = new ElectionDistrict[numDistricts]; // 现在可正常执行

    for (int i = 0; i < numDistricts; ++i) {
        char name[100];
        int voters, numParties;

        std::cout << "Enter the name of district " << i + 1 << ": ";
        std::cin >> name;

        std::cout << "Enter the number of voters in " << name << ": ";
        std::cin >> voters;

        std::cout << "Enter the number of parties in " << name << ": ";
        std::cin >> numParties;

        districts[i] = ElectionDistrict(name, voters, numParties);

        for (int j = 0; j < numParties; ++j) {
            std::string partyName;
            int votes;

            std::cout << "Enter the name of party " << j + 1 << " in " << name << ": ";
            std::cin >> partyName;

            std::cout << "Enter the number of votes for " << partyName << " in " << name << ": ";
            std::cin >> votes;

            districts[i].setPartyVotes(j, votes);
            districts[i].setPartyName(j, partyName);
        }
    }

    // 保存结果到文件
    for (int i = 0; i < numDistricts; ++i) { 
        outFile << districts[i].getName() << " " << districts[i].getVotersCount() << " " << districts[i].getPartiesCount();
        for (int j = 0; j < districts[i].getPartiesCount(); ++j) {
            outFile << " " << districts[i].getPartyVotes()[j] << " " << districts[i].getPartyNames()[j];
        }
        outFile << std::endl;
    }
    outFile.close();

    // 打印所有选区的选举结果
    std::cout << "\n===== 选举结果汇总 =====" << std::endl;
    for (int i = 0; i < numDistricts; ++i) {
        districts[i].printResults();
    }

    delete[] districts; // 释放内存

    return 0;
}

说明 #

• 添加默认构造函数后，动态数组的初始化可正常完成；
• 实现深拷贝的拷贝构造和赋值运算符，避免内存泄漏和重复释放问题；
• 新增getWinningParty()成员函数遍历得票数据，找出得票最高的政党；
• 新增printResults()成员函数负责打印选区的详细结果；
• 保留了原有的文件保存功能，同时添加了结果打印逻辑。

内容的提问来源于stack exchange，提问作者Dodo