LeetCode-in-Java
1399. Count Largest Group
Easy
You are given an integer n.
Each number from 1 to n is grouped according to the sum of its digits.
Return the number of groups that 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.
Constraints:
1 <= n <= 104
Solution
public class Solution {
public int countLargestGroup(int n) {
int largest = 0;
int[] map = new int[37];
int sumOfDigit = 0;
for (int i = 1; i <= n; i++) {
if (i % 10 == 0) {
// reset and start a new sum
sumOfDigit = getSumOfDigits(i);
} else {
sumOfDigit++;
}
int val = ++map[sumOfDigit];
largest = val > largest ? val : largest;
}
return countLargestGroup(largest, map);
}
private int countLargestGroup(int largest, int[] arr) {
int count = 0;
for (int val : arr) {
if (val == largest) {
count++;
}
}
return count;
}
private int getSumOfDigits(int num) {
int sum = 0;
while (num > 0) {
sum += num % 10;
num /= 10;
}
return sum;
}
}