java实现二分查找

public class BinarySearch {

public static void main(String[] args) {
int[] a = { 1, 3, 5, 6, 7, 8, 9, 11, 12, 13 };
System.out.println(search2(a, 1));
System.out.println(search2(a, 3));
System.out.println(search2(a, 5));
System.out.println(search2(a, 6));
System.out.println(search2(a, 7));
System.out.println(search2(a, 8));
System.out.println(search2(a, 9));
System.out.println(search2(a, 11));
System.out.println(search2(a, 12));
System.out.println(search2(a, 13));
System.out.println(search2(a, 100));
System.out.println(search2(a, 10));
System.out.println(search2(a, 0));
}

// 递归算法
public static int search(int[] data, int left, int right, int des) {
if (left > right)
return -1;
int middle = (left + right) / 2;
if (des < data[middle])
return search(data, left, middle - 1, des);
else if (des > data[middle])
return search(data, middle + 1, right, des);
else
return middle;
}

// 非递归算法
public static int search2(int[] data, int des) {
int left = 0;
int right = data.length - 1;
int middle = (left + right) / 2;
while (left <= right/* && left < data.length && right >= 0 */) {
if (data[middle] > des) {
right = middle - 1;
middle = (left + right) / 2;
} else if (data[middle] < des) {
left = middle + 1;
middle = (left + right) / 2;
} else
return middle;
}
return -1;
}
}