数组的线性查找跟二分查找算法

 

package algorithm;

public class Search {

public static void main(String[] args) {
int[] array = { 20, 44, 48, 55, 62, 66, 74, 88, 93, 99 };
int result = binarySearch(90, array);
System.out.println(result);
}

//基本类型的线性查找
public static int linearSearch(int target, int[] array) {
for (int i = 0; i < array.length; i++) {
if (array[i] == target)
return i;
}
return -1;
}

//对象的情况的线性查找
public static int linearSearch(Object target, Object[] array) {
for (int i = 0; i < array.length; i++) {
if (array[i].equals(target))
return i;
}
return -1;
}

//基本类型的二分查找
public static int binarySearch(int target, int[] array) {
int low = 0;
int high = array.length - 1;
while (low <= high) {
int middle = (low + high) / 2;
if (array[middle] == target) {
return middle;
} else if (array[middle] < target) {
low = middle + 1;
} else
high = middle - 1;
System.out.println("low=" + low);
System.out.println("high=" + high);
System.out.println("middle=" + middle);
System.out.println("====================");
}
return -1;
}

//对象情况下的二分查找
public static int binarySearch(Object target, Object[] array) {
int low = 0;
int high = array.length - 1;
while (low <= high) {
int middle = (low + high) / 2;
int result = ((Comparable) array[middle]).compareTo(target);
if (result == 0) {
return middle;
} else if (result < 0) {
low = middle + 1;
} else
high = middle - 1;
}
return -1;
}
}

结果:

low=5
high=9
middle=4
====================
low=8
high=9
middle=7
====================
low=8
high=7
middle=8
====================
-1