Question

同时添加超过13个元素，结果似乎不正确！我的代码如下！添加12个元素时，结果为

NO.0为0
  NO.1是1
  NO.2是2
  NO.3是3
  NO.4是4
  NO.5是5
  NO.6是6
  NO.7是7
  NO.8是8
  NO.9是9   NO.10是10
  NO.11是11

当再添加一个时，结果会发生很大变化，我不知道这里发生了什么：

NO.0为0
  NO.1是1
  NO.2是2
  NO.3是3
  NO.4是4
  NO.5是5
  NO.6是6
  NO.7是7
  NO.8是0
  NO.9是1
  NO.10是2
  NO.11是3
  NO.12是12

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

typedef struct dynarray myarray;
struct dynarray {
    int size;
    int length;
    int *array;
};

myarray *create(void) {
    /* TODO: define for arrays */
    myarray *da;
    da = malloc(sizeof(myarray));
    da->size = 0;
    da->length = 3;
    da->array = (int *)malloc(da->length * sizeof(int));
    return da;
}


void add(myarray *array, int val) {
    int i;
    int length = array->length;
    int size = array->size;
    int *temp;
    //printf("da->size1 = %d\nda->length1 = %d\n",array->size,array->length);

    if (size == length) {
        temp = (int *)malloc(length * sizeof(int));
        for (i = 0; i<size; i++) {
            temp[i] = array->array[i];
            printf("%d,", array->array[i]);
        }


        //printf("!@#$@#$=%d\n",array->length);

        array->array = (int*)realloc(array->array, sizeof(int)*length);
        for (i = 0; i<size; i++)
            array->array[i] = temp[i];
        array->length *= 2;
        length *= 2;
    }
    if (size <length) {
        array->array[size] = val;
        printf("array[%d]====%d\n", size, array->array[size - 1]);
        array->size++;
    }
}


int main() {
    int i;
    myarray *da = create();
    //printf("da->size = %d\nda->length = %d\n",da->size,da->length);

    for (i = 0; i<12; i++)
        add(da, i);
    // printf("a->size = %d\nda->length = %d\n",da->size,da->length);
    for (i = 0; i<12; i++)
        printf("the NO.%i is %d\n", i, da->array[i]);
}

Answer 1

如评论中所述，您正在滥用realloc而不是正确编辑长度。这是添加应该是什么：

void add(myarray *array, int val){
    int length = array->length;
    int size = array->size;

    if(size == length){
        array->length *= 2;
        array->array=(int*)realloc(array->array,sizeof(int)*length);
    }
    array->array[size] = val;
    array->size++;
}

Answer 2

上一个答案中的realloc()不正确，因为它使用旧的长度值
还有一些malloc()和realloc()项检查丢失（可以返回NULL）
realloc()不需要复制

这是我写的代码：

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

#define INIT_LENGTH 3

typedef struct dynarray {
    int size;
    int length;
    int *array;
} myarray;

myarray *create(void) {
    myarray *da;

    da = (myarray *)malloc(sizeof(myarray));
    if (da != NULL)
    {
        da->size = 0;
        da->length = INIT_LENGTH;
        da->array = (int *)malloc(da->length * sizeof(int));
        if (da->array == NULL) {
            free(da);
            da = NULL;
        }
    }
    return da;
}

void add(myarray *da, int val) {
    int size = da->size;
    int length = da->length;
    int *ra = da->array;

    if (size == length) {
        length *= 2;
        ra = (int *)realloc(da->array, length * sizeof(int));
    }
    if (ra != NULL) {
        da->array = ra;
        da->length = length;
        da->array[size] = val;
        da->size++;
    }
    else {
        puts("Warning: failed to realloc() extra space, array size unchanged");
    }
}

int main() {
    int i;
    myarray *da = create();

    if (da == NULL) {
        puts("Initial alloc failure");
        exit(1);
    }

    //printf("da->size = %d\nda->length = %d\n",da->size,da->length);

    for(i = 0; i < 12; i++)
        add(da,i);
    // printf("a->size = %d\nda->length = %d\n",da->size,da->length);
    for(i = 0; i < 12; i++)
        printf("the NO.%i is %d\n", i, da->array[i]);
}

我的动态数组有问题

2 个答案: