数据结构与算法——归并排序

基本思路：

源代码：

/*************************************************************************
> File Name: merge_sort.cpp
> Author:
> Mail:
> Created Time: 2016年01月11日 星期一 15时16分26秒
************************************************************************/

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
using namespace std;

template<class T>
void merge(vector<T> & a, vector<T> & tmpArray, int leftPos, int rightPos, int rightEnd)
{
int leftEnd = rightPos - 1;
int tmpPos = leftPos;
int numElements = rightEnd - leftPos + 1;

while(leftPos <= leftEnd && rightPos <= rightEnd){
if(a[leftPos] <= a[rightPos])
tmpArray[tmpPos++] = a[leftPos++];
else
tmpArray[tmpPos++] = a[rightPos++];
}

while(leftPos <= leftEnd)
tmpArray[tmpPos++] = a[leftPos++];

while(rightPos <= rightEnd)
tmpArray[tmpPos++] = a[rightPos++];

for (int i = 0; i < numElements; i++, rightEnd--)
a[rightEnd] = tmpArray[rightEnd];
}

template<class T>
void mergeSort(vector<T> &a, vector<T> & tmpArray, int left, int right)
{
if (left < right){
int center = (left+right)/2;
mergeSort(a, tmpArray, left, center);
mergeSort(a, tmpArray, center+1, right);
merge(a, tmpArray, left, center+1, right);
}
}

template<class T>
void mergeSort(vector<T> & a)
{
vector<T> tmpArray(a.size());

mergeSort(a, tmpArray, 0, a.size()-1);
}

int main()
{
vector<int> v;
v.push_back(12);
v.push_back(8);
v.push_back(3);
v.push_back(8);
v.push_back(10);
v.push_back(1);
v.push_back(2);
v.push_back(14);
v.push_back(15);
v.push_back(9);
v.push_back(7);
v.push_back(4);

cout << "v: ";
copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
cout << endl;

mergeSort(v);

cout << "mergeSorted v: ";
copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
cout << endl;

return 0;
}