二维数组查找矩阵中的列总和，“使用未初始化的局部变量”

Question

#include <iostream>
#include <iomanip>
using namespace std;

void mArray(int a[3][3])
{
    int row, col;
    cout << "enter row :";
    cin >> row;
    cout << "enter column";
    cin >> col;
    cout << "enter elements";
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cin >> a[i][j];
        }
    }
    cout << endl << endl;
    cout << "matrix is: " << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cout << a[i][j] << " " << endl;
        }
        cout << endl;
    }
    cout << endl << endl;
}
void print(int a[3][3])
{
    int row, col, sum = 0;
    cout << "sum of all column:" << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            sum = sum + a[j][i];
        }
        cout << "sum of column is" << sum << endl;
        sum = 0;

    }
}
int main()
{
    int a[3][3];
    mArray(a);
    print(a);
}

我正在尝试制作一个二维数组矩阵，它可以让您输入数字，然后将列和行相加。但是，我收到一条错误消息，指出变量“col”和“row”未初始化。但是当我尝试将它们设置为 0 时，总和不会相加。有什么办法可以解决这个问题吗？

Answer 1

在此函数中，

void print(int a[3][3])
{
    int row, col, sum = 0;
    cout << "sum of all column:" << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        //...         

您在 for 循环中使用未初始化的变量 row 和 col。

此外，此函数定义

void mArray(int a[3][3])
{
    int row, col;
    cout << "enter row :";
    cin >> row;
    cout << "enter column";
    cin >> col;
    cout << "enter elements";
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        //...

没有意义，因为参数 a 被声明为具有 3 列的数组，但在函数内，由于这些提示，列数可能会有所不同，

    cout << "enter row :";
    cin >> row;
    cout << "enter column";
    cin >> col;

而不是可以具有不同行数和列数的数组需要使用容器 std::vector> 因为 C++ 不支持变长数组。

否则，您将需要动态分配数组数组。

Answer 2

下面的代码正常工作。

#include <iostream>
#include <iomanip>
using namespace std;

void mArray(int *a,int row,int col)
{
    // int row, col;
    cout << "enter row :";
    cin >> row;
    cout << "enter column :";
    cin >> col;
    cout << "enter elements : "<<endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            scanf("%d", ((a+i*col) + j));
        }
    }
    cout << endl << endl;
    cout << "matrix is: " << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cout << *((a+i*col) + j) << " ";
        }
        cout << endl;
    }
    cout << endl << endl;
}
void print(int *a,int row,int col)
{
    int sum = 0;
    cout << "sum of all column:" << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            sum = sum + *((a+i*col) + j);
        }
        cout << "sum of column is : " << sum << endl;
        sum = 0;

    }
}
int main()
{
    int a[3][3];
    mArray((int *)a, 3, 3);
    print((int *)a, 3, 3);
}

但是编写此预绘的更好方法是。

#include <iostream>
#include <iomanip>
using namespace std;

void mArray(int *a,int row,int col)
{
    cout << "enter elements : "<<endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            scanf("%d", ((a+i*col) + j));
        }
    }
    cout << endl << endl;
    cout << "matrix is: " << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cout << *((a+i*col) + j) << " ";
        }
        cout << endl;
    }
    cout << endl << endl;
}
void print(int *a,int row,int col)
{
    int sum = 0;
    cout << "sum of all column:" << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            sum = sum + *((a+i*col) + j);
        }
        cout << "sum of column is : " << sum << endl;
        sum = 0;

    }
}
int main()
{
    int m, n;
    cout << "enter row :";
    cin >> m;
    cout << "enter column :";
    cin >> n;
    int a[m][n];
    mArray((int *)a, m,n);
    print((int *)a, m, n);
}