leetcode 34. Find First and Last Position of Element in Sorted Array

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

Your algorithm's runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

Example 1:

Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]

Example 2:

Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]

实现：二分查找

class Solution {
    public int[] searchRange(int[] nums, int target) {
        int[] ret={-1,-1};
        int left=0,right=nums.length-1;
        while(left<=right){
            int mid=(left+right)/2;
            if(nums[mid]==target){
                left=right=mid;
                while(left>=0&&nums[left]==target){
                    left--;
                }
                while(right<=nums.length-1&&nums[right]==target){
                    right++;
                }
                ret[0]=left+1;
                ret[1]=right-1;
                return ret;
            }else if(nums[mid]<target){
                left=mid+1;
            }else{
                right=mid-1;
            }
        }
        return ret;        
    }
}