题解 | 二分查找-I

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param nums int整型一维数组
     * @param target int整型
     * @return int整型
     */
    public int search (int[] nums, int target) {
        // write code here
        return binarySearch(nums, 0, nums.length - 1, target);
    }

    public int binarySearch(int[] nums, int l, int r, int target) {
        int mid = (l + r) / 2;
        while (l <= r) {
            mid = (l + r) / 2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[mid] > target) {
                r = mid - 1;
            } else if (nums[mid] < target) {
                l = mid + 1;
            }
        }
        return -1;
    }

    public int binarySearch2(int[] nums, int l, int r, int target) {
        int lRes = -1, rRes = -1;
        if (l == r) {
            return target == nums[l] ? l : -1;
        } else if (l < r) {
            int mid = (l + r) / 2;
            lRes = binarySearch2(nums, l, mid, target);
            rRes =  binarySearch2(nums, mid + 1, r, target);
        }
        return lRes != -1 ? lRes : rRes;
    }
}