Hard: Sherlock and valid string

Question: Given a string, Sherlock considers it valid if all the characters in the string occur the same number of time. However, a string is also valid if the frequencies are same after removing any one character.

Example 1:
Input: str = “aabbcd”
Output: NO

Example 2:
Input: str = “abcc”
Output: YES

Problem statement

Let’s break down the problem statement.

Sherlock needs to verify if a given string is valid. A string is valid under 2 conditions:

All characters of the string have same frequencies
If you can delete any one character from the string to achieve condition #1.

Solution

<CH.Section>

package main

import (
	"testing"
)

func isValid(s string) string {
	kind := make(map[rune]int)
	for _, ch := range s {
		kind[ch]++
	}

	if len(kind) == 1 {
		return "YES"
	}

	freq := map[int]int{}
	for _, v := range kind {
		freq[v]++

	}
	max := -9999
	mainFreq := 0
	for k, v := range freq {
		if v > max {
			max = v
			mainFreq = k
		}
	}

	hasUniqFreq := false

	for _, freq := range kind {
		if freq != mainFreq {
			if hasUniqFreq || freq-mainFreq != 1 && freq != 1 {
				return "NO"
			} else {
				hasUniqFreq = true
			}
		}
	}
	return "YES"
}

func TestLastIndex(t *testing.T) {
	tests := []struct {
		input string
		want  string
	}{
		{input: "aabbc", want: "YES"},
		{input: "aabbcd", want: "NO"},
		{input: "abcdefghhgfedecba", want: "YES"},
	}
	for _, tt := range tests {
		if got := isValid(tt.input); got != tt.want {
			t.Errorf("isValid(%v) = %v, want %v", tt.input, got, tt.want)
		}
	}
}

Try it yourself https://go.dev/play/p/jtD3sCn5LkJ </CH.Section>