_1399.java

packagecom.fishercoder.solutions.secondthousand;

importjava.util.ArrayList;
importjava.util.HashMap;
importjava.util.List;
importjava.util.Map;

/*
 * 1399. Count Largest Group
 *
 * Given an integer n. Each number from 1 to n is grouped according to the sum of its digits.
 * Return how many groups have the largest size.
 *
 * Example 1:
 * Input: n = 13
 * Output: 4
 * Explanation: There are 9 groups in total, they are grouped according sum of its digits of numbers from 1 to 13:
 * [1,10], [2,11], [3,12], [4,13], [5], [6], [7], [8], [9]. There are 4 groups with largest size.
 *
 * Example 2:
 * Input: n = 2
 * Output: 2
 * Explanation: There are 2 groups [1], [2] of size 1.
 *
 * Example 3:
 * Input: n = 15
 * Output: 6
 *
 * Example 4:
 * Input: n = 24
 * Output: 5
 *
 * Constraints:
 * 1 <= n <= 10^4
 * */
publicclass_1399 {
publicstaticclassSolution1 {
publicintcountLargestGroup(intn) {
Map<Integer, List<Integer>> map = newHashMap<>();
for (inti = 1; i <= n; i++) {
intsumOfDigits = getSum(i);
if (!map.containsKey(sumOfDigits)) {
map.put(sumOfDigits, newArrayList<>());
 }
map.get(sumOfDigits).add(i);
 }
intmax = 0;
for (intkey : map.keySet()) {
max = Math.max(max, map.get(key).size());
 }
intcount = 0;
for (intkey : map.keySet()) {
if (map.get(key).size() == max) {
count++;
 }
 }
returncount;
 }

privateintgetSum(intnum) {
intsum = 0;
while (num != 0) {
sum += num % 10;
num /= 10;
 }
returnsum;
 }
 }
}