使用OOP在C 中添加矩陣

以下代碼沒有給出正確的輸出。矩陣資料顯示完美，但添加兩個物件 M1 和 M2 后，它沒有顯示正確的輸出。如果我使用 setData 在矩陣中輸入資料，資料會完美存盤，但加法執行不正確。請向我建議如何糾正這個邏輯錯誤？

#include <iostream>
#include <string.h>
using namespace std;

class Matrix{
    private:
        void Allocate();
        int noOfRows;
        int noOfColumns;
        int **data;
    public:
        Matrix(int noOfRows, int noOfColumns);
        void setData();
        void displayData();
        ~Matrix();
        Matrix (const Matrix &ref);
        Matrix operator   (const Matrix &m);
        void operator = (const Matrix &M );
        Matrix& operator = (int x);
};

Matrix::Matrix(int inr=0, int inc=0){
    noOfRows=inr; noOfColumns=inc;
    Allocate();
}

Matrix::Matrix (const Matrix &ref){
    Allocate();
    for(int r=0;r<ref.noOfRows;r  )
        for(int c=0;c<ref.noOfColumns;c  )
            data[r][c]=ref.data[r][c];
}

void Matrix :: operator = (const Matrix &M ) { 
    Allocate();
        noOfRows = M.noOfRows;
        noOfColumns = M.noOfColumns;
        data=M.data;
      }

Matrix& Matrix :: operator = (int x){
    Allocate();
    for(int r=0;r<noOfRows;r  )
        for(int c=0;c<noOfColumns;c  )
            data[r][c]=x;
        return *this;
      }

void Matrix::Allocate(){
    data=new int*[noOfRows];
    for(int i=0;i<noOfRows;i  )
        data[i]=new int[noOfColumns]();
}

void Matrix::setData(){
    for(int r=0;r<noOfRows;r  ){
        for(int c=0;c<noOfColumns;c  ){
            cout<<"Enter ...";cin>>data[r][c];
        }
    cout<<endl; 
    }
}

Matrix Matrix::operator   (const Matrix &m){
    Matrix ms(m.noOfRows,m.noOfColumns);
    for (int i=0; i<m.noOfRows; i  ) 
        for (int j=0; j<m.noOfColumns; j  )
        ms.data[i][j] = data[i][j] m.data[i][j];
    
    return ms;
    }

void Matrix::displayData(){
    for(int r=0;r<noOfRows;r  ){
        for(int c=0;c<noOfColumns;c  )
            cout<<data[r][c]<<"\t";
        cout<<endl;
    }
}

Matrix::~Matrix(){
    for (int i = 0; i < noOfRows;   i)
        delete[] data[i];
    delete [] data;
}

int main(){
    Matrix M3(2,2);M3=0;
    Matrix M1(2,2);M1=1;
    Matrix M2(2,2);M2=2;
//M1.setData();M2.setData();M3.setData();   
    cout<<"\n Matrix A = "<<endl;
    M1.displayData();
    cout<<"\n Matrix B = "<<endl;
    M2.displayData();
    cout<<"\n Matrix C = "<<endl;
    M3 = M1;
    M3.displayData();
    cout<<"\n Sum of Matrix = "<<endl;
    M3 = M1   M2;
    M3.displayData();

    return 0;
}

輸出在這里了解詳細資訊

uj5u.com熱心網友回復：

復制建構式和賦值運算子都被破壞了。讓我們快速瀏覽一下，看看出了什么問題

Matrix::Matrix (const Matrix &ref){
    // noOfRows and noOfColumns have not been initialized. Their values are unknown so 
    // the rest of this function is a crapshoot. Could do anything.
    Allocate();
    for(int r=0;r<ref.noOfRows;r  )
        for(int c=0;c<ref.noOfColumns;c  )
            data[r][c]=ref.data[r][c];
}

// An assignment operator is expected to return Matrix &
void Matrix :: operator = (const Matrix &M ) { 
    // noOfRows and noOfColumns have not been updated. Could be wrong, resulting in 
    // allocate allocating the wrong amount of storage. Moot point since this 
    // allocation is never used. See below.
    Allocate();
        noOfRows = M.noOfRows;
        noOfColumns = M.noOfColumns;
        data=M.data; // both instances share M's data. This will fail sooner or later
                     // If the program lives long enough, both instances will go out
                     // of scope and double delete the allocation.
                     // Also leaks allocation pointed at by `data`.
      }

我很著急，所以我沒有考慮修復賦值運算子，只是使用了 Copy and Swap Idiom。很有可能有更有效的解決方案，但復制和交換通常足夠快，幾乎不可能出錯。這是一個很好的起點，基準測驗會告訴您是否存在問題。

Matrix::Matrix(const Matrix &ref):
        noOfRows(ref.noOfRows),
        noOfColumns(ref.noOfColumns) // initialize row and columns
{
    Allocate(); // now safe to use
    for (int r = 0; r < ref.noOfRows; r  )
        for (int c = 0; c < ref.noOfColumns; c  )
            data[r][c] = ref.data[r][c];
}

Matrix& Matrix::operator =(Matrix M) // correct return type, and does the heavy
                                     // lifting with the copy constructor
{
    std::swap(noOfRows, M.noOfRows);
    std::swap(noOfColumns, M.noOfColumns);
    std::swap(data, M.data);
    return *this;
}

標籤：C 哎呀 指针 矩阵 赋值运算符

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