二分查找

/*
 * 【二分查找要求】：1.必须采用顺序存储结构 2.必须按关键字大小有序排列。
 * */
public class BinarySearchDemo {
    public static void main(String[] args) {
        int[] src = new int[] {1, 3, 5, 7, 8, 9};   
        System.out.println(binarySearch(src, 3));
    }

    private static int binarySearch(int[] src, int des) {
        int low = 0;
        int high = src.length - 1;
        while ( low <= high ) {
            int middle = ( low + high ) / 2;
            if ( des == src[middle]) {
                return middle;
            } else if ( des < src[middle]) {
                high = middle - 1;
            } else {
                low = middle + 1;
            }
            
        }
        return -1;
    }

}