1399

1399. Count Largest Group (Easy)

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

Related Topics:
Array

Solution 1.

// OJ: https://leetcode.com/problems/count-largest-group/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(N)
class Solution {
public:
    int countLargestGroup(int n) {
        unordered_map<int, int> m;
        for (int i = 1; i <= n; ++i) {
            int sum = 0, x = i;
            while (x) {
                sum += x % 10;
                x /= 10;
            }
            m[sum]++;
        }
        int maxSize = 0;
        for (auto &p : m) {
            maxSize = max(maxSize, p.second);
        }
        int ans = 0;
        for (auto &p : m) {
            if (p.second == maxSize) ++ans;
        }
        return ans;
    }
};