c++ - 动态分配的矩阵读取不正确

Question

我想把一个数组的内容放在一个矩阵中。如果矩阵是静态的，一切正常，但当我尝试动态分配时，读取不正常。

int main() 
{ 
int a[]={2, 1, 2, 4, 9, 2, 1, 7, 3, 5, 8, 3};

int c[3][4];

int **b;
b = (int**) malloc (3*sizeof(int*));
for (int i=0; i < 3; i++)
    b[i] = (int*) calloc (4, sizeof(int)); //o linie

int k=0, m=0;
for (int i=0; i<12; i++)
    {
        b[k][m]=a[i];
        c[k][m]=a[i];
        m++;
        if((i!=0) && (!(i % 4))) {k++; m=1;}
    }

for (int i=0; i<3; i++){
    cout << endl;
    for (int j=0; j<4; j++)
        cout << b[i][j] << " ";
}

cout << endl;

for (int i=0; i<3; i++){
    cout << endl;
    for (int j=0; j<4; j++)
        cout << c[i][j] << " ";
}
 return 0;
}


  The output:
  2 1 2 4
  0 1 2 7 //I have 0, why don't I have 9?
  0 5 8 3 //I have 0, why don't I have 3?

  2 1 2 4
  9 1 2 7 //here is correct
  3 5 8 3 //here is correct

请告诉我我哪里错了。

Answer 1

你应该把你的if改成

if (i % 4 == 3)