我写了一段计算矩阵的转置矩阵的程序，运行虽然没有报错，但是我觉得我程序里是不是有两个错误？
（1）验证了if( AT == NULL )之后，没必要再验证if( AT[i] == NULL )吧？属于多此一举；
（2）定义**XT后缺少生成2行5列的全零矩阵的步骤。程序这次虽然没有出错，但容易出现内存地址被占用的情况？
有没有大牛给指点两句？谢谢

#include <stdlib.h>  
#include <stdio.h>
#include <math.h>

double ** Mat_tra(double **A,int Row_A,int Line_A)
//子函数：计算矩阵A的转置矩阵AT，
{
    double **AT;//创建A的转置矩阵
    int i,j;
    AT=(double**)calloc(Line_A,sizeof(double*)); //
    if( AT == NULL )
        {
            printf( "内存分配失败\n" );
            return 0;
        }
    else
        {};
    for(i=0;i<Line_A;i++)  
        {  
            AT[i]=(double*)calloc(Row_A,sizeof(double));//
            if( AT[i] == NULL )
                {
                    printf( "内存分配失败\n" );
                    return 0;
                }        
            else
                {};  
            for(j=0;j<Row_A;j++)
                 {  
                     AT[i][j]=A[j][i];
                 }
        }
    return AT;    
}

void Print_mat(double **A,int Row_A,int Line_A)
//子函数：打印数组
{
    int i,j;
     for(i=0;i<Row_A;i++)//    
         {  
            for(j=0;j<Line_A;j++)
                {  
                    printf("%5.3g  ",A[i][j]);
                    if(Line_A!=1)
                    //如果 Line_A==1，则会出现除以0的情况，子函数会不报错就退出；
                        {
                            if ((j!=0)&(j%(Line_A-1)==0) )  
                            printf("\n");
                         }
                     else
                         {
                             printf("\n");
                         }                  
                }
         }
     printf("\n");    
}

int main()
{
    
    double **X,**XT;
    int i,j;
    int Row_X=2;
    int Line_X=5;
    int Row_XT=5;
    int Line_XT=2;
    
    X=(double**)calloc(Row_X,sizeof(double*));
    if( X == NULL )
      {
          printf( "内存分配失败\n" );
          return 0;
      }
    else
      {};
    
    for(i=0;i<Row_X;i++)//    
    {
        X[i]=(double*)calloc(Line_X,sizeof(double));
        if( X[i] == NULL )
            {
                printf( "内存分配失败\n" );
                return 0;
            }
        else
            {};
        for(j=0;j<Line_X;j++)
            {
                X[i][j]=i+j*j;              
            }        
    }
    
    XT=Mat_tra(X,Row_X,Line_X);
    //将X转置并复制到指针XT标识的内存中    
    Print_mat(X,Row_X,Line_X);
    Print_mat(XT,Row_XT,Line_XT);
    return 0;
}
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