使用带数组的指针时遇到麻烦

Question

I'm new to C and having a problem with pointers. I've been unable to find the answer online or through my peers, so here I am.

I've been given an assignment to:

• Create an array of 20 random integers
• print out the integers
• sort the array in ascending order
• print it out again

When I compile the program with GCC and run, I get a segmentation fault. I've narrowed it down to happening when I try and set the value of number[i] or number[k] in the sort function. Any help would be appreciated.

#include <stdio.h>

void sort(int* number, int n){
     /*Sort the given array number , of length n*/
    int temp, min;
    int i, k;
    for(i=0; i<n; i++){
        min = i;
        for(k=i+1; k<n; k++){
            if(number[k]<min){
                min = k;
            }
        }
        temp = number[i];
        number[i] = number[k];
        number[k] = temp;
    }   
}

int main(){
    /*Declare an integer n and assign it a value of 20.*/
    int n=20;

    /*Allocate memory for an array of n integers using malloc.*/
    int *array = malloc(n * sizeof(array));

    /*Fill this array with random numbers, using rand().*/
    srand(time(NULL));
    int i;
    for(i=0; i<n; i++){
        array[i] = rand()%1000+1;
    }

    /*Print the contents of the array.*/
    for(i=0; i<n; i++){
        printf("%d\n", array[i]);
    }

    /*Pass this array along with n to the sort() function of part a.*/
    sort(&array, 20);

    /*Print the contents of the array.*/
    printf("\n");
    for(i=0; i<n; i++){
        printf("%d\n", array[i]);
    }

    return 0;
}

Here are the compile errors I get:

Q3.c: In function âmainâ:

Q3.c:31: warning: implicit declaration of function âmallocâ

Q3.c:31: warning: incompatible implicit declaration of built-in function âmallocâ

Q3.c:34: warning: implicit declaration of function âsrandâ

Q3.c:34: warning: implicit declaration of function âtimeâ

Q3.c:37: warning: implicit declaration of function ârandâ

Q3.c:46: warning: passing argument 1 of âsortâ from incompatible pointer type

Q3.c:9: note: expected âint *â but argument is of type âint **â

Answer 1

At the point where you swap elements,

temp = number[i];
number[i] = number[k];
number[k] = temp;

k == n because it's after the end of

for(k=i+1; k<n; k++){

You meant to use min instead of k in the swap.

In main ,

int *array = malloc(n * sizeof(array));

allocates enough space for n pointers to int , not space for 20 int . That should be

int *array = malloc(n * sizeof *array);

With regard to the compiler warnings/errors,

#include <stdlib.h>

and call

sort(array, 20);

instead of passing &array .

Answer 2

array是一个int* ，你的sort函数期望一个int* ，你传递&array ，int指针的地址