How to add elements to an array in the C language?

In the C language, the size of an array is fixed and cannot be directly added to. However, you can achieve the effect of adding elements to an array by creating a new array and copying the elements from the original array and the new element into the new array. The specific steps are as follows:

1. Declare the original array and a new element: Assume the original array is arr and the new element is newElement.
2. Create a new array called newArr with a size one more than the original array arr: int newArr[length + 1];
3. Copy the elements from the original array ‘arr’ to the new array ‘newArr’ by iterating through a for loop, assigning the value of ‘arr[i]’ to ‘newArr[i]’.
4. Add the new element newElement to the last position in the new array newArr: assign the value of newElement to newArr[length].
5. Replace the original array arr with a new array newArr by assigning the address of newArr to arr, like this: arr = newArr;.
6. Free the memory of the original array “arr” by using the “free()” function to release the memory space pointed to by “arr”.

Here is a sample code:

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

int main() {
    int length = 5; // 原数组的大小为5
    int *arr = (int *)malloc(length * sizeof(int)); // 动态分配内存
    int newElement = 6; // 新元素的值为6

    // 初始化原数组arr
    for (int i = 0; i < length; i++) {
        arr[i] = i + 1;
    }

    // 创建一个新的数组newArr，大小为原数组arr的大小加1
    int *newArr = (int *)malloc((length + 1) * sizeof(int));

    // 复制原数组arr的元素到新数组newArr中
    for (int i = 0; i < length; i++) {
        newArr[i] = arr[i];
    }

    // 在新数组newArr的最后一个位置添加新元素newElement
    newArr[length] = newElement;

    // 使用新数组newArr替换原数组arr
    arr = newArr;

    // 输出新数组arr的元素
    for (int i = 0; i < length + 1; i++) {
        printf("%d ", arr[i]);
    }

    // 释放原数组arr的内存
    free(arr);

    return 0;
}

Running the above code will output: 1 2 3 4 5 6, indicating that the new element 6 was successfully added to the array arr.