归并排序（2路）

 

 

#include <iostream>#include <ctime>using namespace std;//将两个较小的子问题合并成一个较大的问题void Merge(int a[],int b[],int left,int m,int right);//将大问题分解为较小的问题:2路归并void MergeSort(int a[],int b[],int left,int right){if(left < right){int i = left+(right-left)/2; //取二路分割点MergeSort(a,b,left,i); MergeSort(a,b,i+1,right);Merge(a,b,left,i,right); //将a中已经排好序的两半(以i为分割点)合并到数组b中//将数组b复制回原数组a中for(int i=left;i<=right;i++)a[i] = b[i];}}void Merge(int a[],int b[],int left,int m,int right){int i = left;int j = m+1;int k = left;while(i<=m && j<=right){if(a[i] <= a[j])b[k++] = a[i++];elseb[k++] = a[j++];}while(i<=m)b[k++] = a[i++];while(j<=right)b[k++] = a[j++];}int main(){int N;cout<<"Input N:";cin>>N;int *a = new int[N];int *b = new int[N];srand((unsigned)time(NULL));for(int i=0;i<N;i++){a[i] = rand();cout<<a[i]<<" ";}cout<<endl<<endl;//归并排序MergeSort(a,b,0,N-1);//显示排序后的数组for(int i=0;i<N;i++)cout<<a[i]<<" ";cout<<endl;delete []a;delete []b;return 0;}