Leetcode 1854. Maximum Population Year

Posted 2021-09-13 SnailTyan

文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

2. Solution

**解析：**Version 1，创建一个统计年份人数数组，遍历所有日志，遍历出生、死亡之间的年份，累加对应年份的人口，最后找出人口最多最早的年份，注意边界值。Version 2是遍历所有年份，再遍历所有日志，统计每个年份的人口并比较，比Version 1要慢一些。Version 3根据出生年份和死亡年份来更新当年的人口变化，出省年份人口数量加1，死亡年份人口数量减1，最后遍历所有年份，累加每个年份的人口变化即为当前年份的总人口，注意，此时2050年死亡人口要减1，因此边界值要变为end - start + 1。

• Version 1

class Solution:
    def maximumPopulation(self, logs: List[List[int]]) -> int:
        start = 1950
        end = 2050
        stat = [0] * (end - start)
        for birth, death in logs:
            for i in range(birth, death):
                stat[i - start] += 1
        temp = 0
        for index, count in enumerate(stat):
            if count > temp:
                result = index
                temp = count
        return result + start

• Version 2

class Solution:
    def maximumPopulation(self, logs: List[List[int]]) -> int:
        start = 1950
        end = 2050
        temp = 0
        for i in range(start, end):
            count = 0
            for birth, death in logs: 
                if birth <= i and i < death:
                    count += 1
            if count > temp:
                temp = count
                result = i
        return result

• Version 3

class Solution:
    def maximumPopulation(self, logs: List[List[int]]) -> int:
        start = 1950
        end = 2050
        stat = [0] * (end - start + 1)
        for birth, death in logs:
            stat[birth - start] += 1
            stat[death - start] -= 1
        temp = 0
        current = 0
        for index, count in enumerate(stat):
            current += count
            if current > temp:
                result = index
                temp = current
        return result + start

Reference

1. https://leetcode.com/problems/maximum-population-year/