在C++中实现无STL和无类的最小堆

Implementing minimum heap without STL and classess in C++

本文关键字：STL C++ 实现      更新时间：2023-10-16

我必须将文件中的所有数据(整数(读取到数组中，然后迭代数组以生成最小堆，并将它们添加到当前堆的最后一个元素之后。在读入数组后，我必须对每个元素调用SiftUp()，这意味着将int移动到数组中的正确位置。此外，我必须在读取整数时对其进行计数，并将全局heapSize设置为该值。在所有输入的最后，我试图打印出最小堆数组的前五个元素。输出错误。我的代码没有生成任何最小堆，这就是为什么输出是随机的。逻辑出了什么问题？

输入文件有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);
}
}

为什么要使用数组作为已经全局定义的参数传递。我已尝试修复您的代码。看看吧，照原样做吧。希望它能起作用。

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);
}

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);
}
}
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