本篇内容介绍了“探索数据库的实现原理”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
归并连接的思想与归并排序的思想类似，详见代码注释.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "merge_sort.h"
void merge_array(int array[],int low,int middle,int high)
{
//左边数组的大小(middle在左边数组中,加1)
int n1 = middle - low + 1;
//右边数组的大小
int n2 = high - middle;
//printf("---- merge_array : low = %d,high = %d,middle = %d.\n",low,high,middle);
//初始化左右两边数组
int left[n1],right[n2];
for(int i = 0;i < n1;i++)
left[i] = array[low+i];
for(int i = 0;i < n2;i++)
right[i] = array[middle+i+1];
//归并
int i=0,j=0,k=low;
//同时遍历左右两边数组,较小值进入到结果数组中(回填)
for(;i < n1 && j < n2;)
if(left[i] < right[j])
array[k++] = left[i++];
else
array[k++] = right[j++];
//处理数组中剩余的其他元素
while(i < n1)
array[k++] = left[i++];
while(j < n2)
array[k++] = right[j++];
// printf("--- merge_array : ---\n");
// print_array(array+low,n1 + n2);
}
void merge_arraybyrange(int array[],int low,int high)
{
if (low >= high)
return;//低位置大于等于高位值,退出
//取中间位置
int middle = (low + high)/2;
//printf("---- merge_sort : low = %d,high = %d,middle = %d.\n",low,high,middle);
//对左边数组进行排序
merge_arraybyrange(array,low,middle);
//对右边数组进行排序
merge_arraybyrange(array,middle+1,high);
//两边数组排序完毕后,归并两边的数组
merge_array(array,low,middle,high);
// printf("--- merge_sort : ----\n");
// print_array(array+low,high - low + 1);
}
void merge_sort_recursion(array *tmparr)
{
int low = 0;
int high = tmparr->counter - 1;
merge_arraybyrange(tmparr->arr,low,high);
}
void merge_twoarrays2one(array *a,array *b,array *c)
{
int i=0,j=0;
c->counter=-1;
for(;i < a->counter && j < b->counter;)
{
//归并排序,任意一个数组结束则循环结束
if(a->arr[i] < b->arr[j])
{
c->arr[++c->counter] = a->arr[i++];
}
else
{
c->arr[++c->counter] = b->arr[j++];
}
}
//处理余下的数据
while(i < a->counter)
{
c->arr[++c->counter] = a->arr[i++];
}
while(j < b->counter)
{
c->arr[++c->counter] = b->arr[j++];
}
//从0开始计数,counter+1
c->counter++;
}
void merge_sort(array *tmparr)
{
//临时数组
int tmp[tmparr->counter];
//临时数组（缓存）
array buffer;
buffer.arr = tmp;
for(int i=1;i < tmparr->counter;i=i*2)
{
//i=每次比较的数量=2^x = 1/2/4/8...
for(int j=0;j < tmparr->counter;j+=i*2)
{
//j=比较起始位置,每次比较i个数
if(j+i >= tmparr->counter)
break;
array arr1,arr2;
//指向比较的位置(数组1)
arr1.arr = tmparr->arr+j;
arr1.counter = i;
//指向比较的位置(数组2)
arr2.arr = tmparr->arr+j+i;
arr2.counter = i;
//数组2的数量,判断以免越界
if(j+i*2 >= tmparr->counter)
arr2.counter = tmparr->counter - (j + i);
//归并数组1&2
merge_twoarrays2one(&arr1,&arr2,&buffer);
// printf("---------- i = %d,j = %d,counter = %d\n",i,j,buffer.counter);
// print_array(buffer.arr,buffer.counter);
//归并好的数据拷贝到tmparr中
memcpy(tmparr->arr+j,buffer.arr,buffer.counter*sizeof(int));
}
// printf("------------ i = %d\n",i);
// print_array(tmparr->arr,tmparr->counter);
}
}运行输出
ethanhe@DESKTOP-V73MH70 /d/yunpan/work/Z-SRC/sort
$ /d/tmp/test.exe
--------- test_merge -----------
item[0] is 1
item[1] is 5
item[2] is 10
item[3] is 21
item[4] is 30
item[5] is 40
item[6] is 99
item[7] is 100
item[8] is 200
item[9] is 301
item[10] is 400
--------- test_merge by recursion-----------
item[0] is 1
item[1] is 5
item[2] is 10
item[3] is 21
item[4] is 30
item[5] is 40
item[6] is 99
item[7] is 100
item[8] is 200
item[9] is 301
item[10] is 400“探索数据库的实现原理”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注亿速云网站，小编将为大家输出更多高质量的实用文章！
