插入元素插入C编程动态字符数组 [英] Insert element into dynamic char array in C programming

问题描述

我试图元素添加到C编程动态字符数组时，有一些问题。这里是预期的输出结果：

I was having some problem when trying to add element to dynamic char array in C programming. Here is the expected output:

How many characters do you want to input: 5
Input the string:datas
The string is: datas
Do you want to 1-insert or 2-remove or 3-quit?: 1
What is the character you want to insert: a
Resulting string: adata

我已经做在主要功能的用户输入部分，这里是主的code，我走在字符串输入，大小，并通过他们来插入（）：

I already did those user input part in the main function and here is the code in main where I take in the string input, size and pass them to insert():

printf("How many characters do you want to input: ");
scanf("%d", &n);
str = malloc(n + 1);
printf("Input the string class: ");
scanf("%s", str);

case '1':
    printf("What is the character you want to insert: ");
    scanf(" %c", &input);
    insert(str, input, n);
    break;

和部分在我的插入（）：

And the part where my insert():

void insert(char *str, char input, int n) {
int i;
size_t space = 1;
for (i = 0; i < n; i++) {
    str[i] = (char)(input + i);
    space++;                       
    str = realloc(str, space); 
    if (i > 2) {
        break;
    }
}

for (i = 0; i < n; i++) {
    printf("%c", str[i]);
}
}

然而，当我试图打印出从插入（）的字符串，比方说我进入'A'将追加到动态数组的一个尺寸的第一要素5，那我得到的结果是 ABCD =

However, when I tried to print out the string from insert(), let's say I entered 'a' to append to the first element of dynamic array with a size of 5, the result that I am getting is abcd=

我从<引用href=\"http://stackoverflow.com/questions/5905379/how-would-you-add-chars-to-an-array-dynamically-without-the-array-being-$p$pdefi\">stackoverflow螺纹，我不知道如何解决这个问题。先谢谢了。

I referenced from the stackoverflow thread and I not sure how to fix this. Thanks in advance.

推荐答案

下面是code - 与主叫方的自由位合同！主叫方与称它为插入（安培; STR，输入，N）

Here is the code - with the contract that the caller does the free bit! The caller calls it with insert(&str, input, n)

void insert(char **str, char input, int n) {

char* temp = *str;
int i;

*str = realloc(*str, n + 2); /* realloc first */

if(!*str) /* realloc failed */
{
    fputs("realloc failed", stderr);
    free(temp); /* Free the previously malloc-ed memory */
    exit(-1); /* Exit the program */
}

for (i = n; i >= 0; i--) {
    (*str)[i + 1] = (*str)[i]; /* Move all characters up */ 
}

(*str)[0] = input; /* Insert the new character */

printf("%s", *str); /* Print the new string */
}

很抱歉的格式。是留给读者。我没有检查的算法，但是这并不能泄漏内存

Sorry about the formatting. That is left to the reader. I have not checked the algorithm but this does not leak memory

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