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二分查找的递归与非递归实现
二分查找也称为折半查找,首先,假设表中元素是按升序排列,将表中间位置记录的关键字与查找关键字比较,如果两者相等,则查找成功;否则利用中间位置记录将表分成前、后两个子表,如果中间位置记录的关键字大于查找关键字,则进一步查找前一子表,否则进一步查找后一子表。重复以上过程,直到找到满足条件的记录,使查找成功,或直到子表不存在为止,此时查找不成功。
思想比较简单,话不多说,直接上代码:
/*
* 二分查找,递归与非递归实现
*/
public class binarySearch {
public static void main(String[] args) {
// TODO Auto-generated method stub
int a[] = {11,13,15,22,45,67,88,99,100,140};
int key1 = bsResursion(a, 0, a.length-1, 99);
System.out.println(key1);
int key2 = bs(a, 45);
System.out.println(key2);
}
public static int bs(int a[],int key) { //非递归实现
int low = 0;
int hight = a.length - 1;
while(low < hight) {
int middle = (low + hight) / 2;
if(a[middle] == key) {
return middle;
}else if(a[middle] < key) {
low = middle + 1;
}else if(a[middle] > key) {
hight = middle - 1;
}
}
return -1;
}
public static int bsResursion(int a[], int low, int hight, int key) { //递归实现
if(low > hight) {
return -1;
}
int middle = (low + hight) / 2;
if(a[middle] == key) {
return middle;
}else if(key > a[middle]) {
return bsResursion(a, middle+1, hight, key);
}else if(key < a[middle]) {
return bsResursion(a, low, middle-1, key);
}
return -1;
}
}
运行结果: