1536. 在排序数组中查找元素的第一个和最后一个位置

class Solution:
    """
    @param nums: the array of integers
    @param target: 
    @return: the starting and ending position
    """
    def searchRange(self, nums, target):
        # Write your code here.
        #二分法，首先先定位到等于target的位置，然后target两边走，确定起点和终点
        if not nums: return [-1, -1]
        
        #初始化
        x, y = -1, -1 
        length = len(nums)
        start, end = 0, length - 1 
        
        #二分查找
        while start + 1 < end:
            mid = start + (end - start) // 2 
            
            if nums[mid] > target:
                end = mid 
            elif nums[mid] < target:
                start = mid
            else:
                #如果两者相等的话，则开始target找起点和终点
                left, right = mid, mid 
                while left >= 0:
                    if (nums[left] == target):
                        x = left
                    else:
                        break
                    left -= 1 
                
                while right <= length - 1:
                    if (nums[right] == target):
                        y = right
                    else:
                        break
                    right += 1 
                break
        
        return [x, y]

class Solution:
    """
    @param nums: the array of integers
    @param target: 
    @return: the starting and ending position
    """
    def searchRange(self, nums, target):
        # Write your code here.
        #二分法，首先先定位到等于target的位置，然后target两边走，确定起点和终点
        if not nums: return [-1, -1]
        
        #初始化
        x, y = -1, -1 
        length = len(nums)
        start, end = 0, length - 1 
        left, right = 0, length - 1 
        
        #二分查找
        while start + 1 < end:
            mid = start + (end - start) // 2 
            
            if nums[mid] > target:
                end = mid 
            elif nums[mid] < target:
                start = mid
            else:
                left, right = mid, mid
                break
        
        if nums[start] == target:
            left, right = start, start 
        elif nums[end] == target:
            left, right = end, end 
        
        #如果两者相等的话，则开始target找起点和终点
        while left >= 0:
            if (nums[left] == target):
                x = left
            else:
                break
            left -= 1 
        
        while right <= length - 1:
            if (nums[right] == target):
                y = right
            else:
                break
            right += 1 
        
        return [x, y]