《C和指针》TOP11 为一个指定的数组分配内存并排序处理。

malloc_and_qsort_array.c

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

int comp(const void *, const void *);

int main()
{
    int     *array;
    int     n_values;
    int     i;

    printf("How many values are there?");
    if(scanf("%d", &n_values) != 1 || n_values <= 0) {
        printf("Illegal number of values.\n");
        exit(EXIT_FAILURE);
    }

    //分配内存用于存储
    array = malloc( n_values * sizeof( int ) );
    if (array == NULL) {
        printf("Can't get memory for that many values.\n");
        exit(EXIT_FAILURE);
    }

    //初始化数组元素
    for(i = 0; i < n_values; i++) {
        printf("? ");
        if(scanf("%d", array + i) != 1) {
            printf("Error reading value #%d\n", i);
            free(array);        // 记得退出前要释放
            exit(EXIT_FAILURE);
        }
    }

    //排序
    qsort(array, n_values, sizeof(int), comp);

    //print
    for(i = 0; i < n_values; i++) {
        printf("%d\n", array[i]);
    }

    //释放内存并退出
    free(array);
    return EXIT_SUCCESS;
}

int comp(const void *a, const void *b)
{
    register int const *pa = a;
    register int const *pb = b;
    return *pa > *pb ? 1 : *pa < *pb ? -1 : 0;
}