BinarySearch2

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package com.lab1.test3;

public class BinarySearch2 {
    public static void main(String[] args) {
        int[] a = { 1, 2, 3, 4, 5 };
        int key = 3;
        System.out.println(rank(key, a));
    }

    private static int rank(int key, int[] a) {
        return rank(key, a, 0, a.length - 1);
    }

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

输出

2

Happy learning !!