歸併排序和無序數組的歸併排序

一、將兩個有序數組歸併排序

#include <stdio.h>
#include <stdlib.h>

int main()
{
	int a[5],b[8],c[13];    //不失一般性，兩個數組的長度不一樣長
	int i,j,k,flag=0;
	for(i=0;i<5;i++)
	{
		scanf("%d",&a[i]);	//按排好序，從小到大
	}
	for(i=0;i<8;i++)
	{
		scanf("%d",&b[i]);
	}

	//merge_sort,時間複雜度O(n)
	k=i=j=0;
	while(1)
	{
		if(a[i]<=b[j])
			c[k++]=a[i++];
		else
			c[k++]=b[j++];

		if(i==5)
		{
			flag=1;
			break;
		}
		if(j==8)
		{
			flag=2;
			break;
		}
	}

	if(flag==1)
        while(k<13)
            c[k++]=b[j++];
    if(flag==2)
		while(k<13)
            c[k++]=a[i++];

	for(i=0;i<13;i++)
		printf("%d ",c[i]);
	return 0;
}

 二、將一個數組採用歸併排序的方式排序

       使用遞歸的方式，分治的策略

#include<stdio.h>
#include<stdlib.h>

void MergeArray(int a[],int first,int mid,int last,int temp[]);
void MergeSort(int a[],int first,int last,int temp[]){
    if(first<last){
        int mid = (first + last)/2;
        MergeSort(a,first,mid,temp);
        MergeSort(a,mid+1,last,temp);
        MergeArray(a,first,mid,last,temp);
    }
}

void MergeArray(int a[],int first,int mid,int last,int temp[]){
    int i = first;
    int m = mid;
    int j = mid+1;int n = last;
    int k = 0;

    while(i<=m &&j<=n){
        if(a[i]<a[j])
            temp[k++] = a[i++];
        else
            temp[k++] = a[j++];
    }
    while(i<=m)
        temp[k++] = a[i++];

    while(j<= n)
        temp[k++] = a[j++];
    //更新排序後的原數組
    for (int i = 0; i < k; i++)
    {
        a[i+first] = temp[i];
    }
}


int main()
{
    int a[1000]={6, 2, 4, 1, 5, 9 };
    int temp[100];
    MergeSort(a,0,5,temp);
    int i;
    for(i=0;i<6;i++)
        printf("%d ",a[i]);
    printf("\n");
    return 0;
}