BinarySearch1

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package com.lab1.test3;

public class BinarySearch1 {
    public static void main(String[] args) {
        int[] a = { 1, 2, 3, 4, 5 };
        int key = 3;
        System.out.println(BinarySearch1.indexOf(key, a));
    }

    private static int indexOf(int key, int[] a) {
        int lo = 0;
        int hi = a.length - 1;
        while (lo <= hi) {
            int mid = hi = lo + (hi - lo) / 2;
            if (key < a[mid]) {
                hi = mid - 1;
            } else if (key > a[mid]) {
                lo = mid + 1;
            } else {
                return mid;
            }
        }
        return -1;
    }
}

输出

2

Happy learning !!