LeetCode Entry

1399. Count Largest Group

23.04.2025 easy 2025 kotlin rust

Count of max groups by digits sum 1..n

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Problem TLDR

Count of max groups by digits sum 1..n #easy

Intuition

The brute-force is accepted.

Approach

• max digits sum is 9+9+9+9 = 36

Complexity

• Time complexity: \(O(nlg(n))\)

• Space complexity: \(O(n)\)

Code

    fun countLargestGroup(n: Int): Int =
        (1..n).groupBy { "$it".sumOf { it - '0' }}.values
        .run { count { it.size == maxOf { it.size }}}

    fun countLargestGroup(n: Int): Int {
        val f = IntArray(37); var cnt = 0; var gmax = 0
        for (x in 1..n) {
            var s = 0; var y = x
            while (y > 0) { s += y % 10; y /= 10 }
            val g = ++f[s]
            if (g > gmax) { gmax = g; cnt = 1 }
            else if (g == gmax) cnt++
        }
        return cnt
    }

    pub fn count_largest_group(n: i32) -> i32 {
        let (mut f, mut gmax, mut cnt) = ([0; 37], 0, 0);
        for x in 1..=n {
            let (mut s, mut y) = (0, x);
            while y > 0 { s += y as usize % 10; y /= 10 }
            f[s] += 1; let g = f[s];
            if g > gmax { gmax = g; cnt = 1 }
            else if g == gmax { cnt += 1 }
        } cnt
    }

    int countLargestGroup(int n) {
        int f[37], gmax = 0, cnt = 0;
        for (;n;n--) {
            int x = n, s = 0;
            while (x) s += x % 10, x /= 10;
            int g = ++f[s];
            if (g > gmax) gmax = g, cnt = 1;
            else if (g == gmax) cnt++;
        } return cnt;
    }