当我试图学习使用realloc和malloc时,n的值设置为0或1(未定义的行为)

我正在编写一个C程序,为一个动态字符串数组创建一个交互式界面。该程序由菜单驱动,并遵循以下步骤:

1. 询问用户数组的初始长度。
2. 将相应的字符串存储到用该长度初始化的动态数组中。
3. 启动菜单循环,提示用户选择五个选项之一: (a) 将字符串添加到数组的末尾, (b) 在数组的开头添加一个字符串, (c) 删除数组索引'x'处的元素(作为输入), (d) 显示阵列的长度, (e) 按顺序显示数组的所有元素。
4. 添加和删除字符串会导致数组的大小调整。
5. 提供第六个选项以关闭菜单驱动的程序,从而终止循环。

代码:

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

typedef struct UserStrings
{
    char in[100];
} input;

int main(void)
{

    int n;
    printf("Enter size of Array, please: \n");
    scanf(" %d", &n);
    input *names = (input *)malloc(n * sizeof(input));

    for (int i = 0; i < n; ++i)
    {
        printf("Enter String Number %d : ", i + 1);
        scanf("%s", names[i].in);
    }

    printf("%d\n",n);
    char temp = ' ';

    while (temp != 'f')
    {
        printf("Enter -a- to add an element at the end of the array\n"
               "Enter -b- to add a string at the beginning of the array\n"
               "Enter -c- to delete an element at an index\n"
               "Enter -d- to display the length of the array\n"
               "Enter -e- to display all elements\n"
               "Enter -f- to terminate this program\n");

        scanf("%s", &temp);

        if (temp == 'a')
        {
            names = (input *)realloc(names, (n + 1)*sizeof(input));
            printf("Enter the string\n");
            scanf("%s", names[n].in);
            ++n;
            printf("%d\n",n);
        }
        else if (temp == 'b')
        {
            names = (input *)realloc(names, (n + 1)*sizeof(input));
            ++n;
            printf("Enter the string\n");

            for (int i = n - 1; i > 0; --i)
            {
                strcpy(names[i].in, names[i - 1].in);
            }
            scanf("%s", names[0].in);
            printf("%d\n",n);
        }

        else if (temp == 'c')
        {
            printf("Enter the index 0-%d: ", n - 1);
            int ind;
            scanf(" %d", &ind);

            if (ind < 0 || ind >= n)
            {
                printf("Invalid index. Please enter a valid index.\n");
                continue; // Skip the rest of the loop iteration
            }

            input *new = (input *)malloc((n - 1) * sizeof(input));

            int flag = 0;
            for (int i = 0; i < n; ++i)
            {
                if (i == ind)
                {
                    flag = 1;
                    continue; // Skip the element at the specified index
                }

                new[i - flag] = names[i];
            }
            free(names);
            names = new;
            new = NULL;
            --n;
            printf("%d\n",n);
        }
        else if (temp == 'd')
        {
            printf("Lenght of the array is %d\n", n);
        }
        else if (temp == 'e')
        {
            for (int i = 0; i < n; ++i)
            {
                printf("%d is : %s \n", i + 1, names[i].in);
            }
        }
        else if (temp == 'f')
        {
            printf("Program terminated!\n");
            return 1;
        }
        else
            printf("PLEASE ENTER IN SMALL CAPS AND CORRECT INPUT\n");
    }
}

我尝试使用printf语句调试代码,其中丢失了n的值。在初始化数组时,它似乎具有预期值。但当我尝试ANY操作后,n的值发生了意外的变化。这是输出。

请帮帮我。

Enter size of Array, please:
2
Enter String Number 1 : A
Enter String Number 2 : B
2 // This is the output of printf. So n is fine here.
Enter -a- to add an element at the end of the array
Enter -b- to add a string at the beginning of the array
Enter -c- to delete an element at an index
Enter -d- to display the length of the array
Enter -e- to display all elements
Enter -f- to terminate this program
e // No elements are printing.
Enter -a- to add an element at the end of the array
Enter -b- to add a string at the beginning of the array
Enter -c- to delete an element at an index
Enter -d- to display the length of the array
Enter -e- to display all elements
Enter -f- to terminate this program
d
Lenght of the array is 0 /* Length of array is 0? In the whole code, I cant spot why n will change using these operations. */