Use pointers to pass multi-dimensional arrays to functions and use pointers to reference and modify multi-dimensional arrays.

Use pointers to pass multi-dimensional arrays to functions and use pointers to reference and modify multi-dimensional arrays.

Define A double type two-dimensional array A and another double empty two-dimensional array B of the same size, write A function to copy data in A to B. And test the program.

 1 #include <stdio.h> 2 void copy_ptr(const double (*s)[12],double (*tar)[12],int row,int col); 3 int main(void){ 4     const double rain[5][12]={ 5         {4.3,4.3,4.3,3.0,2.0,1.2,0.2,0.2,0.4,2.4,3.5,6.6}, 6         {8.5,8.2,1.2,1.6,2.4,0.0,5.2,0.9,0.3,0.9,1.4,7.3}, 7         {9.1,8.5,6.7,4.3,2.1,0.8,0.2,0.2,1.1,2.3,6.1,8.4}, 8         {7.2,9.9,8.4,3.3,1.2,0.8,0.4,0.0,0.6,1.7,4.3,6.2}, 9         {7.6,5.6,3.8,2.8,3.8,0.2,0.0,0.0,0.0,1.3,2.6,5.2}10     },t1[5][12];11     copy_ptr(rain,t1,5,12);12     //printf("%.2f",t1[3][8]);13     return 0;14 }15 void copy_ptr(const double (*s)[12],double (*tar)[12],int row,int col){16     int i,j;17     for(i=0;i<row;i++){18         for(j=0;j<col;j++){19             *(*(tar+i)+j)=*(*(s+i)+j);20         }21     }22 }

In the function prototype and function definition, two-dimensional array parameters are written

double (*s)[12]

This indicates that the function accepts a pointer parameter pointing to an array with 12 double values ). That is, the sub-array.

Because the sub-array itself is a pointer to each single double value, the meaning of double (* s) [12] Here is "s is a pointer, it points to (the step size is 1 double, and the range is 0 ~ 11 pointer) ", and the s step is the total range of the pointer it points.

In summary, a multi-dimensional array actually implies a pointer tree behind the value. Or the pointer chain may be more accurate. When an address is not pointed to, the needle actually does not exist. At a time point, the pointer value path from top to bottom is always unique, so it is chained.