Day10 daily 3 questions (2): count the number of the largest groups

subject ：

Give you an integer n . Please find out from 1  To n Each integer of 10 Hexadecimal represents the sum of digits under （ Add the numbers on each digit ）, Then put the digits and equal numbers in the same group .

Please count the number of numbers in each group , And return the number of groups with the largest number of numbers .

Example 1：

Input ：n = 13
Output ：4
explain ： All in all 9 A set of , take 1 To 13 After summing by digits, these groups are ：
[1,10],[2,11],[3,12],[4,13],[5],[6],[7],[8],[9]. All in all 4 Groups have the most numbers in parallel .
Example 2：

Input ：n = 2
Output ：2
explain ： All in all 2 Size is 1 Group [1],[2].
Example 3：

Input ：n = 15
Output ：6
Example 4：

Input ：n = 24
Output ：5

Tips ：

1 <= n <= 10^4

Ideas ：

about [1, n] Every integer in i, We can calculate its digits and s_i . Create a hash map from digit sum to original digit , For every number i, Make key s_i The corresponding value increases by one . Then we find the largest value in the set of values m, Then traverse the hash table , The statistical value is m The number of .

java Code ：

class Solution {
    public int countLargestGroup(int n) {
        Map<Integer, Integer> hashMap = new HashMap<Integer, Integer>();
        int maxValue = 0;
        for (int i = 1; i <= n; ++i) {
            int key = 0, i0 = i;
            while (i0 != 0) {
                key += i0 % 10;
                i0 /= 10;
            }
            hashMap.put(key, hashMap.getOrDefault(key, 0) + 1);
            maxValue = Math.max(maxValue, hashMap.get(key));
        }
        int count = 0;
        for (Map.Entry<Integer, Integer> kvpair : hashMap.entrySet()) {
            if (kvpair.getValue() == maxValue) {
                ++count;
            }
        }
        return count;
    }
}