main.go

// Source: https://leetcode.com/problems/divide-a-string-into-groups-of-size-k
// Title: Divide a String Into Groups of Size k
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// A string `s` can be partitioned into groups of size `k` using the following procedure:
//
// - The first group consists of the first `k` characters of the string, the second group consists of the next `k` characters of the string, and so on. Each element can be a part of **exactly one** group.
// - For the last group, if the string **does not** have `k` characters remaining, a character `fill` is used to complete the group.
//
// Note that the partition is done so that after removing the `fill` character from the last group (if it exists) and concatenating all the groups in order, the resultant string should be `s`.
//
// Given the string `s`, the size of each group `k` and the character `fill`, return a string array denoting the **composition of every group** `s` has been divided into, using the above procedure.
//
// **Example 1:**
//
// ```
// Input: s = "abcdefghi", k = 3, fill = "x"
// Output: ["abc","def","ghi"]
// Explanation:
// The first 3 characters "abc" form the first group.
// The next 3 characters "def" form the second group.
// The last 3 characters "ghi" form the third group.
// Since all groups can be completely filled by characters from the string, we do not need to use fill.
// Thus, the groups formed are "abc", "def", and "ghi".
// ```
//
// **Example 2:**
//
// ```
// Input: s = "abcdefghij", k = 3, fill = "x"
// Output: ["abc","def","ghi","jxx"]
// Explanation:
// Similar to the previous example, we are forming the first three groups "abc", "def", and "ghi".
// For the last group, we can only use the character 'j' from the string. To complete this group, we add 'x' twice.
// Thus, the 4 groups formed are "abc", "def", "ghi", and "jxx".
// ```
//
// **Constraints:**
//
// - `1 <= s.length <= 100`
// - `s` consists of lowercase English letters only.
// - `1 <= k <= 100`
// - `fill` is a lowercase English letter.
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

import (
	"strings"
)

func divideString(s string, k int, fill byte) []string {
	n := len(s)
	var ans []string

	for i := 0; i < n; i += k {
		ans = append(ans, s[i:min(i+k, n)])
	}

	if last := ans[len(ans)-1]; len(last) < k {
		ans[len(ans)-1] += strings.Repeat(string(fill), k-len(last))
	}
	return ans
}