Multiplying two 2D arrays

问题

so I am having an issue multiplying two 2d arrays together. I am pretty sure that matrixA and matrixB are being stored properly, they are displayed properly when the program is ran. When I try to multiply the 2 arrays together I am getting a long string of a lot of 1's and 0's. Any idea on what could be the problem?

Here is my code:

#include <stdio.h>
#include<conio.h>
#include <stdlib.h>
#include <iostream>

/* Routines called. */
int loadMatrixFromFile(char *filename, int *data);
void showMatrix(int *data, int len);
int makeIdent(int matrixB[5][5], int length);
int matrixA[5][5];
int matrixB[5][5];
int matrixC[5][5];
void multiplyMatrices(int matrixA[5][5], int matrixB[5][5],int matrixC[5][5]);

int main(){
    int len, data[1000];
    len = loadMatrixFromFile("Numbers.txt", data);
    showMatrix(data, len);
    makeIdent(matrixB,len);
    multiplyMatrices(matrixA, matrixB, matrixC);
}

int makeIdent(int matrixB[5][5], int len)
{
    int i,j;
    printf("Matrix B = \n");
    for(i=0;i<5;i++){
           for(j=0;j<5;j++){
                 if(i==j){
                         matrixB[i][j]=1;
                         printf("%d ",matrixB[i][j]);
                 }
                 else{
                     matrixB[i][j]=0;
                     printf("%d ",matrixB[i][j]);
                 }
           }
           printf("\n");
     }
    return matrixB[i][j];
     printf("\n");
}
int loadMatrixFromFile(char *filename, int *data)
{
    FILE *in;
    int len;
    int j;
    in = fopen(filename, "r");
    if (in == NULL) {
        printf("Could not find file: %s \n", filename);
    }
    else {
        printf("Reading numbers...\n");
        fscanf(in, "%d", &len);
        printf("reading %d numbers from file %s ....\n", len, filename);
        for(j=0;j<len;j++) {
            fscanf(in, "%d", data + j);
        }
        fclose(in);
    }
    for(int i = 0; i<5; i++){
        for(int j = 0; j < 5; j++){
                matrixA[i][j] = *data;
        }
    }
    return len;
}
void showMatrix(int *data, int len)
{
    int j;
    int count = 0;
    printf("Showing %d numbers from data array....\n", len);
    printf("Matrix A = \n");
    for(j=0;j<len;j++) {
        printf("%d ", *(data + j));
        count++;
        if(count % 5 == 0){
            printf("\n");
        }
    }
    printf("\n");
}

void multiplyMatrices(int matrixA[5][5], int matrixB[5][5],int matrixC[5][5]){
     int i, n, j;

         printf("\n");
 printf("Matrix A x Matrix B = \n");
 for (i = 0; i<5; i++){
    for (n = 0; n<5; n++){
        for (j = 0; j<5; j++){
            matrixC[i][n] += matrixA[i][j]*matrixB[j][n];
            printf("%d ",matrixC[i][n]);
      }
    }
  }
}

Here is how the text file looks that the array A is being pulled from:

25 

1 2 3 4 5
6 7 8 9 1
2 3 4 5 6
7 8 9 1 2
3 4 5 6 7

回答1:

Seems something wrong here:

matrixA[i][j] = *data;

You should use

matrixA[i][j] = *(data + i*5 + j);

Also, try printing:

printf("%d ",matrixC[i][n]);

inside second loop n (after innermost loop j).

来源：https://stackoverflow.com/questions/18840877/multiplying-two-2d-arrays