/*
數組的查找操作。
有一個有序的數組,將一個數插入到該數組中,
還要保證該數組是有序的。如何獲取該元素在數組中的位置。
*/
class ArrayTest4
{
public static void main(String[] args)
{
//int[] arr = {2,3,8,7,8,6,9};
//int index = getIndex(arr,8);
//System.out.println("index="+index);
int[] arr= {1,3,4,6,7,9};
int index = getIndex2(arr,8);
System.out.println("index="+index);
}
/*
折半查找可以提高效率,但必須保證數組有序
*/
public static int halfsearch(int[] arr,int key)
{
int min,max,mid;
min = 0;
max = arr.length-1;
mid = (max+min)/2;
while(arr[mid] != key)
{
if(key>arr[mid])
min = mid+1;
else if(key<arr[mid])
max = mid-1;
if(min>max)
return -1;
mid = (max+min)/2;
}
return mid;
}
public static int getIndex(int[] arr,int key)
{
for(int x=0;x<arr.length;x++)
{
if(arr[x]==key)
return x;
}
return -1;
}
/*
插入一個元素 保持數組有序
*/
public static int getIndex2(int[] arr,int key)
{
int min = 0,max = arr.length-1,mid;
while(min<=max)
{
mid = (max+min)>>1;
if(key>arr[mid])
min = mid+1;
else if(key<arr[mid])
max = mid-1;
else
return mid;
}
return min;
}
/*
折半的第二種方式
*/
public static int halfsearch2(int[] arr,int key)
{
int min = 0,max = arr.length-1,mid;
while(min<=max)
{
mid = (max+min)>>1;
if(key>arr[mid])
min = mid+1;
else if(key<arr[mid])
max = mid-1;
else
return mid;
}
return -1;
}
}