OI算法复习

 1 #include <iostream>
 2  
 3 using namespace std;
 4  
 5 void Qsort(int a[], int low, int high)
 6 {
 7     if(low >= high)
 8         return;
 9     int first = low;
10     int last = high;
11     int key = a[first];
12     while(first < last)
13     {
14         while(first < last && a[last] >= key)
15             --last;
16         a[first] = a[last];
17         while(first < last && a[first] <= key)
18             ++first;
19          a[last] = a[first];
20     }
21     a[first] = key;
22     Qsort(a, low, first-1);
23     Qsort(a, first+1, high);
24 }

 1 template <typename T>
 2 void MergeSort (T data[], int size)
 3 {
 4     if ( size>1 )
 5     {
 6         //预处理
 7         int mid=size/2;
 8         int numOfleft=mid;
 9         int numOfright=size-mid;
10         T* left=new T[numOfleft];
11         T* right=new T[numOfright];
12         //分
13         std::copy(data, data+numOfleft, left);
14         std::copy(data+numOfleft, data+size, right);
15         MergeSort(left, numOfleft);
16         MergeSort(right, numOfright);
17         //合
18         std::merge(left, left+numOfleft, right, right+numOfright, data);
19         //清理
20         delete[] left;
21         delete[] right;
22     }
23 }

 1 template <typename T>
 2 void heap_down (T data[], int i, const int& size)
 3 {
 4     int p=i*2+1;
 5     while ( p<size )
 6     {
 7         if ( p+1<size )
 8         {
 9             if ( data[p]<data[p+1] )
10                 ++p;
11         }
12         if ( data[i]<data[p] )
13         {
14             std::swap(data[p], data[i]);
15             i=p;
16             p=i*2+1;
17         }
18         else
19             break;
20     }
21 }

 1 template <typename T>
 2 void HeapSort (T data[], int size)
 3 {
 4     int i;
 5     for (i=(size-1)/2; i>=0; --i)
 6         heap_down(data, i, size);
 7     for (i=size-1; i>0; --i)
 8     {
 9         std::swap(data[0], data[i]);
10         heap_down(data, 0, i);
11     }
12 }