Question

在函数中处理了变量后，变量的数组值将永远更改。可以将变量值恢复正常吗？在这种情况下，我使用一个函数对数组中的随机数据进行排序。下面是我的代码：

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

using namespace std;

void swap(int *xp, int *yp)
{
  int temp = *xp;
  *xp = *yp;
  *yp = temp;
}

void selectionSort(int arr[], int n)
{
  int i, j, min_idx;

  for (i = 0; i < n - 1; i++)
  {
    min_idx = i;
    for (j = i + 1; j < n; j++)
    {
      if (arr[j] < arr[min_idx])
      {
        min_idx = j;
      }
    }
    swap(&arr[min_idx], &arr[i]);
  }
}

void insertionSort(int arr[], int n)
{
  int i, key, j;
  for (i = 1; i < n; i++)
  {
    key = arr[i];
    j = i - 1;

    while (j >= 0 && arr[j] > key)
    {
      arr[j + 1] = arr[j];
      j = j - 1;
    }
    arr[j + 1] = key;
  }
}

void bubbleSort(int arr[], int n)
{
  int i, j;
  for (i = 0; i < n - 1; i++)
  {
    for (j = 0; j < n - i - 1; j++)
    {
      if (arr[j] > arr[j + 1])
      {
        swap(&arr[j], &arr[j + 1]);
      }
    }
  }
}

int partition(int arr[], int low, int high)
{
  int pivot = arr[high];
  int i = (low - 1);

  for (int j = low; j <= high - 1; j++)
  {
    if (arr[j] <= pivot)
    {
      i++;
      swap(&arr[i], &arr[j]);
    }
  }
  swap(&arr[i + 1], &arr[high]);
  return (i + 1);
}

void quickSort(int arr[], int low, int high)
{
  if (low < high)
  {
    int pi = partition(arr, low, high);

    quickSort(arr, low, pi - 1);
    quickSort(arr, pi + 1, high);
  }
}

void printArray(int arr[], int size)
{
  int i;
  for (i = 0; i < size; i++)
  {
    cout << arr[i] << " ";
  }
  cout << endl;
}

void merge(int arr[], int l, int m, int r)
{
  int i, j, k;
  int n1 = m - l + 1;
  int n2 = r - m;

  int L[n1], R[n2];

  for (i = 0; i < n1; i++)
  {
    L[i] = arr[l + i];
  }
  for (j = 0; j < n2; j++)
  {
    R[j] = arr[m + 1 + j];
  }

  i = 0;
  j = 0;
  k = l;

  while (i < n1 && j < n2)
  {
    if (L[i] <= R[j])
    {
      arr[k] = L[i];
      i++;
    }
    else
    {
      arr[k] = R[j];
      j++;
    }
    k++;
  }

  while (i < n1)
  {
    arr[k] = L[i];
    i++;
    k++;
  }

  while (j < n2)
  {
    arr[k] = R[j];
    j++;
    k++;
  }
}

void mergeSort(int arr[], int l, int r)
{
  if (l < r)
  {
    int m = l + (r - l) / 2;

    mergeSort(arr, l, m);
    mergeSort(arr, m + 1, r);

    merge(arr, l, m, r);
  }
}

int main()
{
  int select;
  char req;

  int arr[] = {20, 45, 30, 25, 15, 50, 100, 55, 10, 25};
  int arr_size = sizeof(arr) / sizeof(arr[0]);

  do
  {
    system("clear");
    cout << "--- Sorting Menu ---\n\n";
    cout << "1. Selection Sort\n";
    cout << "2. Insertion Sort\n";
    cout << "3. Bubble Sort\n";
    cout << "4. Quick Sort\n";
    cout << "5. Merge Sort\n\n";
    cout << "Choose (1/2/3/4/5) : ";
    cin >> select;

    switch (select)
    {
    case 1:
      system("clear");
      cout << "Selection Sort\n\n";
      cout << "Random data : ";
      printArray(arr, arr_size);
      selectionSort(arr, arr_size);
      cout << "Sorted data : ";
      printArray(arr, arr_size);
      break;
    case 2:
      system("clear");
      cout << "Insertion Sort\n\n";
      cout << "Random data : ";
      printArray(arr, arr_size);
      insertionSort(arr, arr_size);
      cout << "Sorted data : ";
      printArray(arr, arr_size);
      break;
    case 3:
      system("clear");
      cout << "Bubble Sort\n\n";
      cout << "Random data : ";
      printArray(arr, arr_size);
      bubbleSort(arr, arr_size);
      cout << "Sorted data : ";
      printArray(arr, arr_size);
      break;
    case 4:
      system("clear");
      cout << "Quick Sort\n\n";
      cout << "Random data : ";
      printArray(arr, arr_size);
      quickSort(arr, 0, arr_size - 1);
      cout << "Sorted data : ";
      printArray(arr, arr_size);
      break;
    case 5:
      system("clear");
      cout << "Merge Sort\n\n";
      cout << "Random data : ";
      printArray(arr, arr_size);
      mergeSort(arr, 0, arr_size - 1);
      cout << "Sorted data : ";
      printArray(arr, arr_size);
      break;
    default:
      break;
    }
    cout << endl
         << endl;
    cout << "Back to menu ? (Y/n) : ";
    cin >> req;
    if (req != 'Y' || req != 'y')
    {
      system("clear");
      cout << "Exit from this program...\n\n";
    }
  } while (req == 'Y' || req == 'y');

  return 0;
}

Answer 1

在函数中处理了变量后，变量的数组值将永远更改。可以将变量值恢复为正常值吗？

在调用任何函数之前简单地复制它们：

std::vector<int>(arr_size) arr_copy;
std::copy(std::begin(arr), std::end(arr), std::begin(arr_copy));

switch (select)
{
case 1:
  system("clear");
  cout << "Selection Sort\n\n";
  cout << "Random data : ";
  printArray(arr, arr_size);
  selectionSort(arr, arr_size);
  cout << "Sorted data : ";
  printArray(arr, arr_size);

，然后将其复制回去：

  std::copy(std::begin(arr_copy), std::end(arr_copy), std::begin(arr));
  break;

在进入函数之前如何设置先前的数组值？

1 个答案: