function gameOfThrones(key: string): string {
    // 0. define a map, couting [char] in [key]
    let hash = new Map<string, number>()
    for (let c of key) hash.set(c, (hash.get(c) || 0) + 1)
    
    // 1. define some variable
    let key_is_odd: boolean = key.length % 2 != 0
    let flag: boolean = true

    // 2. loop hash and check [char_count] of each [char]...
    for (const char_count of hash.values()) {
        const char_count_is_odd = char_count % 2 != 0
        
        // 2.1 [char_count] that divided by 2, mean it can be split 2 side
        //  -> skip check
        // 2.2 [char_count] that not divided by 2, but [key] is 
        //  -> there is at least one extra char, return NO
        // 2.3 [char_count] and [key] is both odd, it can be have only 1 extra char
        //  -> if have more than 1, return NO
        //  -> set flag = false to know that already have 1
        if (!char_count_is_odd) continue
        if (!key_is_odd) return 'NO'
        if (!flag) return 'NO'

        flag = false
    }

    return 'YES'
}