归并排序

#include<iostream>
using namespace std;

void merge(int *a, int p, int q, int r){
	int m = q + 1;
	int k = p;
	int *b1 = new int[q-p+1];
	int *b2 = new int[r-m+1];

	for(int i = p,j = 0; (i < m)&&(j<q-p+1); i++){
		b1[j++] = a[i];
	}
	for(int i = m, j = 0; (i < r + 1)&&(j<r-m+1); i++){
		b2[j++] = a[i];
	}

	int c1,c2;
	for(c1 = 0, c2 = 0; (c1 < q-p+1) && (c2 < r-m+1);){
		if(b1[c1] > b2[c2]){
			a[k++] = b2[c2];
			c2++;
		}else{
			a[k++] = b1[c1];
			c1++;
		}
	}

	if(c1 < q-p+1){
		for(int i = c1; i < q-p+1; i++){
			a[k++] = b1[i];
		}
	}

	if(c2 < r-m+1){
		for(int i = c2; i < r-m+1 ; i++){
			a[k++] = b2[i];
		}
	}
	
}

void mergeSort(int *a,int p, int r){
	if(p < r){
		int q = (p+r)/2;
		mergeSort(a,p,q);
		mergeSort(a,q+1,r);
		merge(a,p,q,r);
	}
}

void main(){
	int a[] = {2,4,1,121,9,111,8,10,12,0};
	int length = sizeof(a)/sizeof(a[0]);
	mergeSort(a,0,length-1);
	for(int i = 0; i < length; i++){
		cout<<a[i]<<" ";
	}
	cout<<endl;
}

输出结果：