11、归并排序

  1 /*
  2 归并排序，需要多一倍的内存空间
  3 速度和快速排序一样快
  4 */
  5 
  6 #include<iostream>
  7 #include<algorithm>
  8 
  9 using namespace std;
 10 
 11 template<class T>
 12 void MergeSort(T *initlist, T *resultlist, const int l, const int m, const int n)
 13 {
 14     int i1, i2, iresult;
 15     for (i1 = l, i2 = m + 1, iresult = l; i1 <= m && i2 <= n; iresult++)
 16     {
 17         if (initlist[i1] <= initlist[i2])
 18         {
 19             resultlist[iresult] = initlist[i1];
 20             i1++;
 21         }
 22         else
 23         {
 24             resultlist[iresult] = initlist[i2];
 25             i2++;
 26         }
 27     }
 28     std::copy(initlist+i1, initlist+ m+1, resultlist+iresult);//将比较完剩下的放进结果数组
 29     std::copy(initlist+i2, initlist+ n + 1, resultlist+iresult);
 30 
 31 }
 32 
 33 template<class T>
 34 void MergePass(T *initList,T *resultList,const int n,const int s)
 35 {
 36     int i;
 37     for (i = 1; i <= n - 2 * s + 1; i += 2 * s)
 38     {
 39         MergeSort(initList,resultList,i,i+s-1,i+2*s-1);
 40     }
 41     if ((i + s - 1) < n)//有剩余的
 42         MergeSort(initList, resultList, i, i + s - 1, n);
 43     else
 44         copy(initList + i, initList + n + 1, resultList + i);
 45 }
 46 
 47 template <class T>
 48 void Merge(T *a, const int n)
 49 {
 50     T *tempList = new int[n + 1];//tempList[0]不用
 51     for (int l = 1; l < n; l *= 2)
 52     {
 53         MergePass(a,tempList,n,l);
 54         l *= 2;
 55         MergePass(tempList,a,n,l);
 56     }
 57     delete[] tempList;//删除临时数组空间，防止内存泄漏
 58 }
 59 
 60 
 61 int main()
 62 {
 63     int a[] = { 0,23,47,81,95,7,14,39,55,62,74 };
 64     int b[11] = { 0 };
 65     MergeSort(a, b, 1, 4, 10);
 66     for (int i = 1; i < 11; i++)
 67     {
 68         cout << b[i] << " ";
 69     }
 70     cout << endl;
 71 
 72     int m[] = {0,26,5,77,1,61,11,59,15,48,19};
 73     int n[11] = { 0 };
 74     MergePass(m,n,10,1);
 75     cout << "第一次归并：" << endl;
 76     for (int i = 1; i < 11; i++)
 77         cout << n[i] << " ";
 78     cout << endl;
 79 
 80     MergePass(n, m, 10, 2);
 81     cout << "第二次归并：" << endl;
 82     for (int i = 1; i < 11; i++)
 83         cout << m[i] << " ";
 84     cout << endl;
 85 
 86     MergePass(m, n, 10, 4);
 87     cout << "第三次归并：" << endl;
 88     for (int i = 1; i < 11; i++)
 89         cout << n[i] << " ";
 90     cout << endl;
 91 
 92     MergePass(n, m, 10, 8);
 93     cout << "第四次归并：" << endl;
 94     for (int i = 1; i < 11; i++)
 95         cout << m[i] << " ";
 96     cout << endl;
 97 
 98     cout << "上面的都是中间结果的测试" << endl;
 99     cout << "下面开始测试归并排序的最后结果" << endl;
100     int x[] = {0,26,5,77,1,61,11,59,15,48,19};
101     Merge(x,10);
102     for (int i = 1; i < 11; i++)
103         cout << x[i] << " ";
104     cout << endl;
105     system("pause");
106     return 0;
107 }

vs2015中运行结果：