 
void merge_sort(int array[],int first,int end)  
{
	if(first < end){
		int center = (first + end)/2;     //得到中間數(shù)
		merge_sort(array,first,center);   
		merge_sort(array,center+1,end);
	}
}

“并”的實現(xiàn)

按照上面的圖片，我們每排一下序就給它并一下

具體代碼實現(xiàn)

void merge(int array[],int first,int center,int end)
{
 
	int n1 = center - first + 1;
	int n2 = end - center;
	int L[n1+1];
	int R[n2+1];
	for(int i = 0; i < n1; i++ )
	{
		L[i] = array[first+i];     //得到前面一部分?jǐn)?shù)組
	}
	//printArray(L,n1);
	for(int j = 0; j < n2; j++ )
	{
		R[j] = array[center+j+1]; //得到后面一部分?jǐn)?shù)組
	}
	//printArray(R,n2);
	L[n1] = 1000;    //設(shè)置哨兵
	R[n2] = 1000;	 //設(shè)置哨兵
	//cout << "R[5] =" << R[4] << endl;
	int k1 = 0;
	int k2 = 0;
	for (int k = first; k <= end; ++k)    //把得到的兩個數(shù)組進(jìn)行排序合并
	{	
		//cout << L[k1] <<endl;
		//cout << R[k2] <<endl;
		if(L[k1] <= R[k2])
		{	
			//cout << L[k1] <<endl;
			array[k] = L[k1];
			//cout << array[k] << endl;
			//cout << "k1 =" << k1 << endl;
			k1 = k1 + 1; 
		}else{
			//cout << R[k2] <<endl;
			array[k] = R[k2];
			//cout << array[k] << endl;
			//cout << "k2 =" << k2 << endl;
			k2 = k2 + 1; 
		}
		//cout << array[k] <<endl;
	}
	//printArray(array,10);
}

加到“分”函數(shù)里

因為我們分完了要并，所以我們把“并”函數(shù)寫進(jìn)“分”函數(shù)里

void merge_sort(int array[],int first,int end)  
{
	if(first < end){
		int center = (first + end)/2;     //得到中間數(shù)
		merge_sort(array,first,center);   
		merge_sort(array,center+1,end);
		merge(array,first,center,end);
	}
}

完整代碼

加上int main()就行

#include <iostream>
using namespace std;
 
/*
* 打印數(shù)組
*/
void printArray(int array[],int length)
{
	for (int i = 0; i < length; ++i)
	{
		cout << array[i] << endl;
	}
}
 
/*
* 一個數(shù)組從中間分成兩個有序數(shù)組
* 把這兩個有序數(shù)組合并成一個有序數(shù)組
*/
void merge(int array[],int first,int center,int end)
{
 
	int n1 = center - first + 1;
	int n2 = end - center;
	int L[n1+1];
	int R[n2+1];
	for(int i = 0; i < n1; i++ )
	{
		L[i] = array[first+i];     //得到前面一部分?jǐn)?shù)組
	}
	//printArray(L,n1);
	for(int j = 0; j < n2; j++ )
	{
		R[j] = array[center+j+1]; //得到后面一部分?jǐn)?shù)組
	}
	//printArray(R,n2);
	L[n1] = 1000;    //設(shè)置哨兵
	R[n2] = 1000;	 //設(shè)置哨兵
	//cout << "R[5] =" << R[4] << endl;
	int k1 = 0;
	int k2 = 0;
	for (int k = first; k <= end; ++k)    //把得到的兩個數(shù)組進(jìn)行排序合并
	{	
		//cout << L[k1] <<endl;
		//cout << R[k2] <<endl;
		if(L[k1] <= R[k2])
		{	
			//cout << L[k1] <<endl;
			array[k] = L[k1];
			//cout << array[k] << endl;
			//cout << "k1 =" << k1 << endl;
			k1 = k1 + 1; 
		}else{
			//cout << R[k2] <<endl;
			array[k] = R[k2];
			//cout << array[k] << endl;
			//cout << "k2 =" << k2 << endl;
			k2 = k2 + 1; 
		}
		//cout << array[k] <<endl;
	}
	//printArray(array,10);
}
 
/*
* 分治算法
* 把一個數(shù)組從中間分成分開
* 然后進(jìn)行排序
*/
void merge_sort(int array[],int first,int end)  
{
	if(first < end){
		int center = (first + end)/2;     //得到中間數(shù)
		merge_sort(array,first,center);   
		merge_sort(array,center+1,end);
		merge(array,first,center,end);
	}
}
 
int main(int argc, char const *argv[])
{
	int array[10] = {0,6,1,2,3,7,8,9,4,5};
	//merge(array,0,4,9);
	merge_sort(array,0,9);
	printArray(array,10);
	//int center = (0 + 9)/2;
	//cout << "center" << center << endl;
	//cout << "hello";
	return 0;
}

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