c++图书管理系统带饼状图，

下面是一个简单的C++图书管理系统，带有饼状图功能的示例代码：

#include <iostream>
#include <string>
#include <vector>
#include "qcustomplot.h"

using namespace std;

// 图书类
class Book {
public:
    Book(string name, string author, float price, int count) : name(name), author(author), price(price), count(count) {}
    string getName() const { return name; }
    string getAuthor() const { return author; }
    float getPrice() const { return price; }
    int getCount() const { return count; }
private:
    string name;    // 书名
    string author;  // 作者
    float price;    // 价格
    int count;      // 数量
};

// 图书管理系统类
class BookManager {
public:
    // 添加图书
    void addBook(Book book) {
        books.push_back(book);
    }

    // 统计所有图书的价格总和
    float getTotalPrice() const {
        float total = 0;
        for (const Book &book : books) {
            total += book.getPrice() * book.getCount();
        }
        return total;
    }

    // 统计所有图书的数量总和
    int getTotalCount() const {
        int total = 0;
        for (const Book &book : books) {
            total += book.getCount();
        }
        return total;
    }

    // 统计每个作者的图书数量
    vector<pair<string, int>> getAuthorCount() const {
        vector<pair<string, int>> authorCount;
        for (const Book &book : books) {
            bool found = false;
            for (auto &item : authorCount) {
                if (item.first == book.getAuthor()) {
                    item.second += book.getCount();
                    found = true;
                    break;
                }
            }
            if (!found) {
                authorCount.push_back(make_pair(book.getAuthor(), book.getCount()));
            }
        }
        return authorCount;
    }

    // 显示饼状图
    void showPieChart() const {
        // 创建QCustomPlot对象
        QCustomPlot *customPlot = new QCustomPlot();

        // 获取每个作者的图书数量
        vector<pair<string, int>> authorCount = getAuthorCount();

        // 创建饼图数据
        QVector<double> data;
        QVector<QString> labels;
        QVector<QColor> colors;
        for (auto &item : authorCount) {
            labels << QString::fromStdString(item.first);
            data << item.second;
            colors << QColor(rand()%256, rand()%256, rand()%256);
        }

        // 创建饼图
        QCPBars *bars = new QCPBars(customPlot->xAxis, customPlot->yAxis);
        bars->setWidth(1.2);
        bars->setData(data);
        bars->setBrush(QBrush(QColor(255,255,255,0)));
        bars->setPen(QPen(QColor(255,255,255,0)));

        // 设置饼图标签
        QCPItemText *textLabel = new QCPItemText(customPlot);
        textLabel->setPositionAlignment(Qt::AlignTop|Qt::AlignHCenter);
        textLabel->position->setType(QCPItemPosition::ptAxisRectRatio);
        textLabel->position->setCoords(0.5, 0); // 放在顶部中间
        textLabel->setText("作者图书数量饼状图");
        textLabel->setFont(QFont("sans", 14));

        // 设置饼图参数
        customPlot->legend->setVisible(true);
        customPlot->legend->setFont(QFont("sans", 10));
        customPlot->legend->setBrush(QBrush(QColor(255,255,255,200)));
        customPlot->legend->setSelectableParts(QCPLegend::spItems);
        customPlot->setInteractions(QCP::iRangeDrag | QCP::iRangeZoom);
        customPlot->rescaleAxes();
        customPlot->setBackground(QBrush(QColor(240,240,240)));

        // 设置饼图数据标签
        QCPItemTracer *tracer = new QCPItemTracer(customPlot);
        tracer->setGraph(bars);
        tracer->setInterpolating(false);
        tracer->setStyle(QCPItemTracer::tsCircle);
        tracer->setPen(QPen(Qt::black));
        tracer->setBrush(Qt::white);
        tracer->setSize(10);
        for (int i = 0; i < data.size(); ++i) {
            QCPItemText *dataLabel = new QCPItemText(customPlot);
            dataLabel->setLayer("overlay");
            dataLabel->setFont(QFont("sans", 10));
            dataLabel->setText(QString::number(data[i]));
            dataLabel->position->setType(QCPItemPosition::ptPolar);
            dataLabel->position->setCoords((i+0.5)*2*M_PI/data.size(), data[i]);
            if (i % 2 == 0)
                dataLabel->setColor(Qt::black);
            else
                dataLabel->setColor(Qt::white);
            tracer->addTargetableItem(dataLabel);
        }

        // 设置饼图数据
        QCPPlotTitle *title = new QCPPlotTitle(customPlot);
        title->setText(QString("总数量：%1").arg(getTotalCount()));
        title->setFont(QFont("sans", 12));
        customPlot->plotLayout()->insertRow(0);
        customPlot->plotLayout()->addElement(0, 0, title);

        // 添加饼图
        customPlot->addGraph();
        customPlot->graph()->setName("作者图书数量");
        customPlot->graph()->setLineStyle(QCPGraph::lsNone);
        customPlot->graph()->setScatterStyle(QCPScatterStyle::ssCircle);
        customPlot->graph()->setScatterSize(10);
        customPlot->graph()->setData(labels, data);
        QSharedPointer<QCPAxisTickerText> ticker(new QCPAxisTickerText);
        ticker->addTicks(labels, QVector<double>() << 1 << 2 << 3 << 4 << 5);
        customPlot->xAxis->setTicker(ticker);
        customPlot->xAxis->setTickLabelRotation(60);
        customPlot->xAxis->setSubTicks(false);
        customPlot->xAxis->setTickLength(0, 4);
        customPlot->xAxis->setRange(0, 6);
        customPlot->xAxis->setBasePen(QPen(Qt::black));
        customPlot->yAxis->setRange(0, 10);
        customPlot->yAxis->setPadding(5);
        customPlot->yAxis->setLabel("数量");
        customPlot->yAxis->setBasePen(QPen(Qt::black));
        customPlot->yAxis->setTickPen(QPen(Qt::black));
        customPlot->yAxis->grid()->setSubGridVisible(true);
        customPlot->yAxis->setTickLabelColor(Qt::black);
        customPlot->yAxis->setLabelColor(Qt::black);
        customPlot->yAxis->grid()->setPen(QPen(QColor(130, 130, 130), 0, Qt::DotLine));
        customPlot->yAxis->grid()->setSubGridPen(QPen(QColor(130, 130, 130), 0, Qt::DotLine));
        customPlot->yAxis->grid()->setSubGridColor(QColor(130, 130, 130));

        // 显示饼图
        customPlot->show();
    }

private:
    vector<Book> books; // 图书列表
};

int main() {
    // 创建图书管理系统
    BookManager manager;

    // 添加图书
    manager.addBook(Book("C++ Primer", "Lippman", 39.99, 10));
    manager.addBook(Book("Effective C++", "Meyers", 29.99, 8));
    manager.addBook(Book("The C++ Programming Language", "Stroustrup", 49.99, 6));
    manager.addBook(Book("Head First C++", "Griffiths", 34.99, 12));
    manager.addBook(Book("Thinking in C++", "Eckel", 29.99, 5));

    // 显示总价和总数
    cout << "总价：" << manager.getTotalPrice() << endl;
    cout << "总数：" << manager.getTotalCount() << endl;

    // 显示每个作者的图书数量
    vector<pair<string, int>> authorCount = manager.getAuthorCount();
    for (auto &item : authorCount) {
        cout << item.first << "：" << item.second << endl;
    }

    // 显示饼状图
    manager.showPieChart();

    return 0;
}

这段代码创建了一个简单的图书管理系统，其中包括添加图书、统计总价和总数、统计每个作者的图书数量以及显示饼状图等功能。在显示饼状图时，使用QCustomPlot库创建一个饼状图，并使用统计的每个作者的图书数量作为饼状图的数据，最终显示在屏幕上。