g1801_1900.s1854_maximum_population_year.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1801_1900.s1854_maximum_population_year;

// #Easy #Array #Counting #2022_05_10_Time_0_ms_(100.00%)_Space_42.7_MB_(24.42%)

/**
 * 1854 - Maximum Population Year\.
 *
 * Easy
 *
 * You are given a 2D integer array `logs` where each logs[i] = [birth_i, death_i] indicates the birth and death years of the i^th person.
 *
 * The **population** of some year `x` is the number of people alive during that year. The i^th person is counted in year `x`'s population if `x` is in the **inclusive** range [birth_i, death_i - 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 <= birth_i < death_i <= 2050
**/
public 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;
    }
}