使用带有指向双指针的指针的scanf（）

I feel like I've attempted every combination I know of to get this to work and can't figure it out. How can I scanf() into an int** passed as a pointer to a function? I tried searching but couldn't find this, if it's a duplicate please let me know and I'll delete. It begins to run and after entering a few values it segfaults.

我觉得我已经尝试过我所知道的每一个组合,让它发挥作用,无法弄明白。如何将scan()转换为作为指向函数的指针传递的int **?我试过搜索但找不到这个,如果它是重复的请告诉我,我会删除。它开始运行,在输入一些值之后就会出现段错误。

Here's my code, I think it's messing up on the scanf() line of the setMatrix() function:

这是我的代码,我认为它搞乱了setMatrix()函数的scanf()行:

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

// create zero initialized matrix
int** callocMatrix(int rmax, int colmax) {  
        int **mat = calloc(rmax, sizeof(int*));
        for(int i = 0; i < rmax; i++) mat[i] = calloc(colmax, sizeof(int));
        return mat;
}

// fill matrix
void setMatrix(int ***mat, int r, int c){
    printf("Insert the elements of your matrix:\n");
    for (int i = 0; i < r; i++) {
        for (int j = 0; j < c; j++) {
            printf("Insert element [%d][%d]: ", i, j);
            scanf("%d", mat[i][j]); // problem here??
            printf("matrix[%d][%d]: %d\n", i, j, (*mat)[i][j]);
        }
    }   
    return;
}

// print matrix
void printMatrix(int ***mat, int r, int c){ 

    for (int i=0; i<r;i++){
        for (int j=0; j<c;j++) {
                printf("%d ", (*mat)[i][j]);
        }
        printf("\n");
    }

}

int main(int argc, char *argv[]) {

    int r = 3, c = 3;

    int **mat = callocMatrix(r, c);

    setMatrix(&mat, r, c);

    printMatrix(&mat, r, c);
}

2 个解决方案

#1

There is no need to use triple pointer ***. Passing two-dimensional array will work as is. Here is the code:

没有必要使用三指针***。传递二维数组将按原样工作。这是代码:

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

// create zero initialized matrix
int** callocMatrix(int rmax, int colmax) {
    int **mat = calloc(rmax, sizeof(int*));
    for(int i = 0; i < rmax; i++) mat[i] = calloc(colmax, sizeof(int));
    return mat;
}

// fill matrix
void setMatrix(int **mat, int r, int c){
    printf("Insert the elements of your matrix:\n");
    for (int i = 0; i < r; i++) {
        for (int j = 0; j < c; j++) {
            printf("Insert element [%d][%d]: ", i, j);
            scanf("%d", &mat[i][j]); // no problem here
            printf("matrix[%d][%d]: %d\n", i, j, mat[i][j]);
        }
    }
}

// print matrix
void printMatrix(int **mat, int r, int c){

    for (int i=0; i<r;i++){
        for (int j=0; j<c;j++) {
                printf("%d ", mat[i][j]);
        }
        printf("\n");
    }
}

int main(int argc, char *argv[]) {

    int r = 3, c = 3;

    int **mat = callocMatrix(r, c);

    setMatrix(mat, r, c);

    printMatrix(mat, r, c);
}

#2

Should be:

scanf("%d", &(*mat)[i][j]);

You're passing a pointer to you matrix object, so you need to dereference it (with *) just as you do with printf. scanf then needs the address of the element to write into, so you need the &

您正在向矩阵对象传递指针,因此您需要将其取消引用(使用*),就像使用printf一样。然后scanf需要写入元素的地址,所以你需要&

#1