Question

我必须将文件中的所有数据（整数）读入数组，然后对数组进行迭代以最小化堆并将其添加到当前堆的最后一个元素之后。读入数组后，我必须在每个元素上调用SiftUp()，这意味着将int移到数组中的正确位置。另外，我在读取整数时必须对整数进行计数，并将全局heapSize设置为该整数。在所有输入的末尾，我试图打印出最小堆数组的前五个元素。输出错误。我的代码没有做任何最小堆，这就是为什么输出是随机的。逻辑有什么问题？

输入文件包含97个整数：

347
765
654
44
15
567
098 
//and so on

输出：

Please enter the name of the file to open :data.txt
 at index 1 :284
 at index 2 :870
 at index 3 :319
 at index 4 :47
 at index 5 :312
 at index 1 :284    // i dont know why it started again
 at index 2 :870
 at index 3 :319
 at index 4 :47
 at index 5 :312     //stops here

我的程序：

using namespace std;

int heapSize;
void SiftUp(int arr[], int heapSize);
const int arr_Size=100;
int heapArr[arr_Size];
void minHeap(int heapArr[]);

int main()
{
    int integers;
    string fileName;
    ifstream infile;
    cout << "Please enter the name of the file to open :";
    cin >> fileName;
    infile.open(fileName.c_str());
    if(!infile)
    {
        cerr << "An eror occurred while openieng the file.";
        exit(1);
    }
    while(!infile.eof())
    {

        for (int i=0; i<arr_Size; i++){
            infile >> integers;
            heapArr[i]=integers;
            heapSize=i;
    }
}
infile.close();
minHeap(heapArr);
for (int count =1 ; count <=5 ; count ++)
{
    cout << " Min at index " << count  <<" :"<< heapArr[count] << endl;
}
return 0;
}

void SiftUp(int arr[], int heapSize)
{
    int p;
    if (heapSize==1) return;
    else p = heapSize/2;
    if (arr[p] > arr[heapSize]) return;
    else swap (arr[heapSize],arr[p]);
    SiftUp(arr, p);
    }

void minHeap(int arr[])
{
    for (int i=0; i <arr_Size ; i++){ 
        SiftUp(arr, heapSize);
    }
}

Answer 1

using namespace std;

int heapSize;
const int arr_Size=100;
int heapArr[arr_Size];
int main()
{
 int integers;
 string fileName;
 ifstream infile;
 cout << "Please enter the name of the file to open :";
 cin >> fileName;
 infile.open(fileName.c_str());
 if(!infile)
 {
     cerr << "An eror occurred while openieng the file.";
     exit(1);
 }
 while(!infile.eof())
 {

     for (int i=0; i<arr_Size; i++){
         infile >> integers;
         heapArr[i]=integers;
         heapSize=i;
 }

 infile.close();
 build_minheap(heapArr,heapSize);
 for (int count =1 ; count <=5 ; count ++)
 {
     cout << " Min at index " << count  <<" :"<< heapArr[count] << endl;
 }
 return 0;
}

void min_heapify(int *a,int i,int n)
{
   int j, temp;
   temp = a[i];
   j = 2 * i;
   while (j <= n)
   {
       if (j < n && a[j+1] < a[j])
           j = j + 1;
       if (temp < a[j])
           break;
       else if (temp >= a[j])
       {
           a[j/2] = a[j];
           j = 2 * j;
       }
   }
  a[j/2] = temp;
  return;
 }
 void build_minheap(int *a, int n)
 {
    int i;
    for(i = n/2; i >= 1; i--)
    {
        min_heapify(a,i,n);
     }
 }

Answer 2

为什么要使用数组作为已全局定义的参数进行传递。我已尝试修正您的代码。看看并照原样进行。希望会成功。

 int main()
{
    int integer;
    string fileName;
    ifstream infile;
    cout << "Please enter the name of the file to open :";
    cin >> fileName;                                                  // asks user to     input filename
    infile.open(fileName.c_str());                                    // opens file
    if(!infile)
    {
    cerr << "An eror occurred while openieng the file.";
    exit(1);
    }
    int i;
    for (i=1; i<arr_Size; i++){
    infile >> integer;
    if(infile.fail())break;
    heapArr[i]=integer;
    SiftUp(i);
    }
    infile.close();
    heapSize=i;
    for (int count =1 ; count <=5 ; count ++)
    {
    cout << count  <<" :"<< heapArr[count] << endl;
    }

    return 0;
}

void SiftUp(int heapSize){
int p;
if (heapSize==1) return;
p = heapSize/2;
if (heapArr[p] < heapArr[heapSize]) return;
swap (heapArr[heapSize],heapArr[p]);
SiftUp(p);
}

在C ++中无需STL和类即可实现最小堆

2 个答案: