为什么 C++ 程序给我地址而不是 MxN 数组 Col-Wise Sum 中的值，但给我 NxN 数组中的值？

Question

#include <iostream>

using namespace std;

int main(){
   int matrix_A[10][10],row, col,csum=0;

   //Getting the rows from user and storing in row
   cout<<"--------------------------"<<endl;
   cout<<"|Enter The Number Of Rows|"<<"\n";
   cout<<"--------------------------"<<endl;
   cin>>row;
   //Getting the columns from user and storing in col
   cout<<"-----------------------------"<<endl;
   cout<<"|Enter The Number Of Columns|"<<"\n";
   cout<<"-----------------------------"<<endl;
   cin>>col;

   /* Asking the user to input the elements of matrix
    * and storing them in the matrix array
    */
   cout<<"---------------------------------------"<<endl;
   cout<<"|Enter The Elements Of The Matrix A Is|"<<endl;
   cout<<"---------------------------------------"<<"\n";
   for(int i =0;i<row;i++) {
     for(int j=0;j<col;j++) {
       cin>>matrix_A[i][j];
     }
   }

// Display column-wise sum of matrix of size m x n
    cout<<"----------------------------------------"<<"\n";
    cout<<"|The Column-Wise Sum Of The Matrix A Is|"<<"\n";
    cout<<"----------------------------------------"<<"\n";
        for(int i=0;i<row;i++)
        {
            csum =0;
            for(int j=0;j<col;j++){
                csum = csum + matrix_A[j][i];
            }
        cout<<csum<<"\t";

}
return 0;
}

只有当我输入方阵 nxn 时，此代码才给我逐列总和的值，但当输入 mxn 矩阵时，它会给我地址。

1.是什么原因？

2.如何让程序在mxn矩阵中赋值？

Answer 1

解决方法是在开始列求和之前转置矩阵

// Display column-wise
    cout<<"----------------------------------------"<<"\n";
    cout<<"|The Column-Wise Sum Of The Matrix A Is|"<<"\n";
    cout<<"----------------------------------------"<<"\n";
// Create transpose of matrix A of size n x m to get column-wise sum like row-wise sum
  for(int i=0;i<row;i++) {
    for(int j=0;j<col;j++) {
      matrix_B[j][i] = matrix_A[i][j];
    }
  }
// Display column-wise sum of matrix of size m x n
  for(int i=0;i<col;i++) {
        csum =0;
    for(int j=0;j<row;j++) {
      cout<<matrix_B[i][j]<<"\t";
    csum = csum + matrix_B[i][j];
      /* This is just to format the output
       * so you can see the matrix format
       * in the output transpose matrix.
       */
      if(j==row-1)
        cout<<"|  "<<csum;
    }
    cout<<"\n\n";
  }

Answer 2

你可以如下使用。

#include <iostream>

using namespace std;

int main(){
   int matrix_A[10][10],row, col, csum=0, rsum = 0;

   //Getting the rows from user and storing in row
   cout<<"--------------------------"<<endl;
   cout<<"|Enter The Number Of Rows|"<<"\n";
   cout<<"--------------------------"<<endl;
   cin>>row;
   //Getting the columns from user and storing in col
   cout<<"-----------------------------"<<endl;
   cout<<"|Enter The Number Of Columns|"<<"\n";
   cout<<"-----------------------------"<<endl;
   cin>>col;

   /* Asking the user to input the elements of matrix
    * and storing them in the matrix array
    */
   cout<<"---------------------------------------"<<endl;
   cout<<"|Enter The Elements Of The Matrix A Is|"<<endl;
   cout<<"---------------------------------------"<<"\n";
   for(int i =0;i<row;i++) {
     for(int j=0;j<col;j++) {
       cin>>matrix_A[i][j];
     }
   }

// Display column-wise sum of matrix of size m x n
    cout<<"----------------------------------------"<<"\n";
    cout<<"|The Column-Wise Sum Of The Matrix A Is|"<<"\n";
    cout<<"----------------------------------------"<<"\n";
        for(int i=0;i<col;i++)
        {
            csum =0;
            for(int j=0; j<row;j++){
                csum += matrix_A[j][i];
            }
        cout<<csum<<"\t";

        }
// Display row-wise sum of matrix of size m x n
    cout<<"----------------------------------------"<<"\n";
    cout<<"|The Row-Wise Sum Of The Matrix A Is|"<<"\n";
    cout<<"----------------------------------------"<<"\n";
        for(int i=0;i<row;i++)
        {
            rsum =0;
            for(int j=0; j<col;j++){
                rsum += matrix_A[i][j];
            }
        cout<<rsum<<endl;

        }
return 0;
}

Answer 3

仅当我输入方阵 nxn 时，此代码才给我逐列总和的值，但当输入 mxn 矩阵时，它会给我地址。

好吧，让我们看看为什么

让row = 3 和col = 2

你的矩阵是

[ 
  [1,2],
  [3,4],
  [6,7]
]

现在在你的循环中

for(int i=0;i<row;i++)
        {
            csum =0;
            for(int j=0;j<col;j++){
                csum = csum + matrix_A[j][i];
            }
        cout<<csum<<"\t";

i 将是 0,1,2

j 将是 0,1

现在什么时候

csum = csum + matrix_A[j][i];

发生。在循环期间，这也会发生：

csum = csum + matrix_A[0][2];

而matrix_A[0][2] 未定义。