34.在排序数组中查找元素的第一个和最后一个位置

二分查找中，寻找 leftIdx 即为在数组中寻找第一个大于等于 target 的下标，寻找 rightIdx 即为在数组中寻找第一个大于 target 的下标，然后将下标减一。进行两次查找

class Solution {
    public int[] searchRange(int[] nums, int target) {
        //寻找左边界
        int leftIndex = search(nums,target);
        if(leftIndex >= nums.length || nums[leftIndex] != target){
            return new int[]{-1,-1};
        }
        //寻找右边界
        int rightIndex = search(nums,target + 1);
        return new int[]{leftIndex, rightIndex - 1};
    }
    private int search(int[] nums, int target) {
        int left = 0;
        int right = nums.length - 1;
        while (left <= right){
            int mid = (right + left) / 2 ;
            if (nums[mid] >= target){
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return left;
    }

}