RandomBox.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

public class RandomBox : MonoBehaviour
{
    Dictionary<string, int> entry = new Dictionary<string, int>();

    public void AddEntry(string _name, int amount)
    {
        if (!entry.TryGetValue(_name, out int previousAmount)) {
            entry[_name] = amount;
        }
        else {
            entry[_name] = previousAmount + amount;
        }
        
        Debug.Log($"{_name}:{entry[_name]}");
    }

    public int Count() => entry.Values.Sum(x => x);

    public float GetPossibility(string _name)
    {
        if (!entry.TryGetValue(_name, out int amount)) {
            return 0;
        }

        return (float) amount / Count();
    }

    public string Pick(bool removePickedItem = false)
    {
        // 더 명백한 확률 유지를 위해서는 미리 픽 어레이를 만들어두고 차례로 뽑는것이 적절함. 
        var entryInstance = new List<string>();
        foreach (var key in entry.Keys) {
            int count = entry[key];
            for (int i = 0; i < count; i++) {
                entryInstance.Add(key);
            }
        }

        int pickedIndex = Random.Range(0, Count() - 1);
        string picked = entryInstance[pickedIndex];
        
        Debug.Log($"{picked} : {GetPossibility(picked) * 100}%");
        if (removePickedItem) {
            if (entry[picked] == 1) {
                entry.Remove(picked);
            }
            else {
                entry[picked] = entry[picked] - 1;
            }

            Debug.Log($"New Possibility {picked} : {GetPossibility(picked) * 100}%");
        }
        
        return picked;
    }
    
    private void Awake()
    {
        AddEntry("Apple", 4);
        AddEntry("Banana", 3);
        AddEntry("Grape", 15);
        Debug.Log($"Banana Possibility : {GetPossibility("Banana") * 100}%");
        AddEntry("Apple", 2);
        Debug.Log($"Banana Possibility : {GetPossibility("Banana") * 100}%");
        Pick(false);
    }
}