LeetCode34. 在排序数组中查找元素的第一个和最后一个位置

思路：二分查找

public class Solution {
    

    public int[] searchRange(int[] nums, int target) {
    
        int l = search2(nums, target);
        int r = search2(nums, target + 1) - 1;
        if (l == nums.length || nums[l] != target) {
    
            return new int[]{
    -1, -1};
        }
        return new int[]{
    l, r};
    }

    public int search2(int[] nums, int target) {
    
        int l = 0, r = nums.length;
        while (l < r) {
    
            int mid = (r + l) / 2;
            if (nums[mid] >= target)
                r = mid;
            else
                l = mid + 1;
        }
        return l;
    }
}