[leetcode] 849. Maximize Distance to Closest Person @ python

原题

In a row of seats, 1 represents a person sitting in that seat, and 0 represents that the seat is empty.

There is at least one empty seat, and at least one person sitting.

Alex wants to sit in the seat such that the distance between him and the closest person to him is maximized.

Return that maximum distance to closest person.

Example 1:

Input: [1,0,0,0,1,0,1]
Output: 2
Explanation:
If Alex sits in the second open seat (seats[2]), then the closest person has distance 2.
If Alex sits in any other open seat, the closest person has distance 1.
Thus, the maximum distance to the closest person is 2.
Example 2:

Input: [1,0,0,0]
Output: 3
Explanation:
If Alex sits in the last seat, the closest person is 3 seats away.
This is the maximum distance possible, so the answer is 3.
Note:

1 <= seats.length <= 20000
seats contains only 0s or 1s, at least one 0, and at least one 1.

解法

双指针法.

代码

class Solution(object):
    def maxDistToClosest(self, seats):
        """
        :type seats: List[int]
        :rtype: int
        """
        left, count, ans = -1, 0, 0
        for i, val in enumerate(seats):            
            if val == 0:
                # count zeros before a person
                count += 1
            else:
                # there is no person in the left
                if left == -1:
                    distance = count
                # there is a person in the left, a person in the right
                else:
                    # if count is odd, distance = (odd + 1)//2
                    distance = (count+1)//2
                # update the left pointer
                left = i
                count = 0
                ans = max(ans, distance)
                
        return max(ans, count)