问题：array1,array2为两个有序的升序数组，将array1和array2合并为一个升序有序数组

1.合并两个有序数组array1,array2，借助数组array3。从头开始，将array1的第一个元素和array2的第一个元素比较，小的放到array3中。

 # include <stdio.h>

# define  MAX 15


//合并两个有序数组a,b，借助数组c
 void  MergeArray(int array1[], int len1, int array2[], int len2, int array3[], int len3)
{
	if (len3 < len1 + len2)
		return;
	int  index1 = 0, index2 = 0, index3 = 0;
	while (index1 < len1&&index2 < len2)
	{
		if (array1[index1] < array2[index2])
		{
			array3[index3++] = array1[index1++];
		}
		else
		{
			array3[index3++] = array2[index2++];
		}
	}
	while (index1 < len1)
	{
		array3[index3++] = array1[index1++];
	}
	while (index2 < len2) 
	{
		array3[index3++] = array2[index2++];
	}
	return;

}


int main()
{
	int array1[] = { 1,3,5,7,9 };
	int array2[] = { 2,4,6,8,9 };
	int len1 = sizeof(array1) / sizeof(int);
	int len2 = sizeof(array2) / sizeof(int);
	int array3[MAX];
	MergeArray(array1, len1, array2, len2, array3, MAX);
	for (int i = 0; i < len1 + len2; i++)
	{
		 printf ("%d ", array3[i]);
	}

}

  

2.假设array1足够大，能够放下array1和array2，从后往前比较array1，和array2，大的元素放到最右边。

 #include<stdio.h>
#define MAX 15
//合并两个有序数组array1,array2,从后往前比较，将array1和array2最后一个元素比较，大的放到len1+len2-1
void MergeArray(int array1[], int len1, int array2[], int len2)
{
	int index1 = len1 - 1;
	int index2 = len2 - 1;
	int index = len1 + len2 - 1;
	while (index1 >= 0&&index2 >= 0)
	{
		if (array1[index1] > array2[index2])
		{
			array1[index--] = array1[index1--];
		}
		else
		{
			array1[index--] = array2[index2--];
		}
	}
	while (index1 >= 0)
	{
		array1[index--] = array1[index1--];
	}
	while (index2 >= 0)
	{
		array1[index--] = array2[index2--];
	}
	return;

}


int main()
{
	int array1[MAX] = {1,3,5,7,9,10 };
	int array2[] = { 2,4,6,8,9 };
	
	int len2 = sizeof(array2) / sizeof(int);
	MergeArray(array1, 6, array2,  len 2);
	for (int i = 0; i < 6 + len2; i++)
	{
		printf("%d ", array1[i]);
	}

}