c++ - 调整动态数组大小时保留用户输入值的问题

Question

这是我尝试创建一个动态数组，该数组在用户为数组预分配数据后调整大小。我使用第二个索引/计数器来获取原始计数器的值。

最具体地说，如何用用户输入的值替换计算机中的随机值？

#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;

int main()
{
    int size;
    cout <`enter code here`< "Enter the size of the array: ";
    cin  >> size;
    if (size <= 0) {
        cout << "Array size must be > 0" << endl;
        exit(0);
    }
    int *arr;
    arr = new int[size];

    int num = 0;
    int idx = 0, idx2 = 0;

    while (num != -1)
    {
        cout << "Enter a value to place into an array or -1 to exit: ";
        cin >> num;
        if (num == -1)
        {
            break;
        }
        else if (idx < size)
        {
            arr[idx++] = num;
        }
        else
        {
            idx2 = idx * 2;
            int *newArr = new int[size];
            memcpy(newArr, arr, size * sizeof(int));
            delete [] arr;
            newArr[idx++] = num;
            arr = newArr;

            /*
             int* temp = new int[length + added];
             memcpy(temp, array, length * sizeof(int));
             memcpy(temp + length, added_array, added * sizeof(int));
             delete[] array;
             array = temp;
             */
        }

    }

    for(int x = 0; x < idx; x++)
    {
        cout <<arr[x] << endl;
    }

    cout << endl  << "Reshaped Array of Size: "<< idx << endl;
    return 0;
}

具体来说，我对大小为 2 的数组的输出错误地显示了我输入的值(2、3、4、5、6、66、55):

3
4
268848517
6
1397644077
55

Reshaped Array of Size: 6
Program ended with exit code: 0

Answer 1

从您的代码，

        else
        {
            idx2 = idx * 2;
            int *newArr = new int[size];               <<<<<<<<<<<<  bug
            memcpy(newArr, arr, size * sizeof(int));   <<<<<<<<<<<<
            delete [] arr;
            newArr[idx++] = num;
            arr = newArr;

有一个错误。您正在创建具有相同“大小”的 int[]。它应该是“idx2”。

+ memcpy() 的拷贝大小应相应更改(例如 idx)