为什么我的矩阵不加？

Question

When I add the matrices, my added matrix output is just zeroes instead of the added numbers. My instructor says the problem may be that I passed the sum as a double pointer instead of a triple pointer to update it, but I don't know how to fix it. What do I do so the matrix numbers sums come out instead of zeroes?

#include <stdio.h>

#include <stdlib.h>



int** make_matrixA(int num_rows, int num_cols){
int** matrixA;
int row, col;
int userNum;


    matrixA = (int**)malloc(num_rows * sizeof(int*));
for(row = 0; row < num_rows; ++row){
    matrixA[row] = (int*)malloc(num_cols * sizeof(int));
}
for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        scanf("%d", &userNum);
    }
}
return matrixA;
}

int** make_matrixB(int num_rows, int num_cols){
int** matrixB;
int row, col;
int userNum;


    matrixB = (int**)malloc(num_rows * sizeof(int*));
for(row = 0; row < num_rows; ++row){
    matrixB[row] = (int*)malloc(num_cols * sizeof(int));
}
for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        scanf("%d", &userNum);
    }
}
return matrixB;
}

int** make_matrixC(int num_rows, int num_cols){
int** matrixC;
int row;


    matrixC = (int**)malloc(num_rows * sizeof(int*));
for(row = 0; row < num_rows; ++row){
    matrixC[row] = (int*)malloc(num_cols * sizeof(int));
}
return matrixC;
}


int** add_matrix(int num_rows, int num_cols, int** matrixA, int** matrixB, int** matrixC){
int row, col;

for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        matrixC[row][col] = matrixA[row][col] + matrixB[row][col];
    }
}
return matrixC;
}

void print_matrix(int num_rows, int num_cols,int** matrixA, int** matrixB, int** matrixC){
int row, col;

printf("A + B = \n");
for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        matrixC[row][col] = matrixA[row][col] + matrixB[row][col];
        printf("%d ", matrixC[row][col]);
    }
    printf("\n");
}
}

void delete_matrixA(int num_rows, int** matrixA){
int row;
for(row = 0; row < num_rows; ++row){
    free(matrixA[row]);
}
free(matrixA);
}

void delete_matrixB(int num_rows, int** matrixB){
int row;
for(row = 0; row < num_rows; ++row){
    free(matrixB[row]);
}
free(matrixB);
}

void delete_matrixC(int num_rows, int** matrixC){
int row;
for(row = 0; row < num_rows; ++row){
    free(matrixC[row]);
}
free(matrixC);
}

int main(){
int num_rows, num_cols;
int** matrixA;
int** matrixB;
int** matrixC;  

//get input
printf("Please enter the number of rows: ");
scanf("%d", &num_rows);
printf("Please enter the number of columns: ");
scanf("%d", &num_cols);     

//make matrix A
printf("Enter Matrix A\n");
matrixA = make_matrixA(num_rows, num_cols);

//make matrix B
printf("Enter Matrix B\n");
matrixB = make_matrixB(num_rows, num_cols);

//add the matrices
matrixC = make_matrixC(num_rows, num_cols);
matrixC = add_matrix(num_rows, num_cols, matrixA, matrixB, matrixC);

//print the matrix
print_matrix(num_rows, num_cols, matrixA, matrixB, matrixC);

//delete the matrices
delete_matrixA(num_rows, matrixA);
delete_matrixB(num_rows, matrixB);
delete_matrixC(num_rows, matrixC);

return 0;
}

Answer 1

Your make_matrix() functions are not good. The code to read numbers

for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        scanf("%d", &userNum);
    }
}

You should do

for(row = 0; row < num_rows; ++row){
    for(col = 0; col < num_cols; ++col){
        scanf("%d", &matrixA[row][col]); //use matrix to store number
    }
}

Change your functions appropriately to use correct variables. without this your code does not store values in matrix and adds up random numbers that are in matrices.