Leetcode 1854. Maximum Population Year

Gary Chiang
1 min readMay 9, 2021



You are given a 2D integer array logs where each logs[i] = [birthi, deathi] indicates the birth and death years of the ith person.

The population of some year x is the number of people alive during that year. The ith person is counted in year x's population if x is in the inclusive range [birthi, deathi - 1]. Note that the person is not counted in the year that they die.

Return the earliest year with the maximum population.

Example 1:

Input: logs = [[1993,1999],[2000,2010]]
Output: 1993
Explanation: The maximum population is 1, and 1993 is the earliest year with this population.

Example 2:

Input: logs = [[1950,1961],[1960,1971],[1970,1981]]
Output: 1960
The maximum population is 2, and it had happened in years 1960 and 1970.
The earlier year between them is 1960.


  • 1 <= logs.length <= 100
  • 1950 <= birthi < deathi <= 2050

[Gary- Java- Hashmap]


  1. use hashmap to count all the exist year
  2. if there is an early year have the same population count, update the year



Gary Chiang

CS new grad, 6 years experience related to supply chain management. Located in Bay area