1854. Maximum Population Year

Problem

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
Explanation: 
The maximum population is 2, and it had happened in years 1960 and 1970.
The earlier year between them is 1960.

  Constraints:

• 1 <= logs.length <= 100

• 1950 <= birthi < deathi <= 2050

Solution (Java)

class Solution {
    public int maximumPopulation(int[][] logs) {
        int[] arr = new int[101];
        for (int[] log : logs) {
            arr[log[0] - 1950]++;
            arr[log[1] - 1950]--;
        }
        for (int i = 1; i < 101; i++) {
            arr[i] += arr[i - 1];
        }
        int maxyear = 1950;
        int max = 0;
        for (int i = 0; i < 101; i++) {
            if (arr[i] > max) {
                max = arr[i];
                maxyear = i + 1950;
            }
        }
        return maxyear;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).