java小程序 实例 二分法查找

使用二分法在一个数组中查找一个数：

package com.test;

public class BinaryFind {


private final static int size = 500000;


public static void main(String[] args) {
int[] a = new int[size];
for (int i = 0; i < size; i++) {
a[i] = i + 1;
}
find(a, -500001155);
}


private static void find(int a[], int n) {
int middle = 0;
int start = 0;
int end = a.length;
try {
while (start < end) {
middle = (start + end) / 2;
if (n == a[middle]) {
System.out.println("找到了" + n);
return;
} else if (n > a[middle]) {
start = middle + 1;
} else {
end = middle - 1;
}
}
} catch (Exception e) {
e.printStackTrace();
System.out.println(start + "|" + end + "|" + middle);
// TODO: handle exception
}

System.out.println("找不到" + n);


}

}

注：数组有序，从大到小，