Weighted Random

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

public class RandomUtility {

    public interface Weighted {
        float getWeight();
    }

    public static T pickWeighted<T>(IList<T> arr, IList<float> weights) {
        float total = weights.Sum ();
        float pick = Random.Range (0.0f, total);
        int idx = 0;
        while (idx < weights.Count-1 && weights[idx] < pick) pick -= weights[idx++];
        return arr[idx];
    }

    public static T pickWeighted<T>(IList<T> arr) where T:RandomUtility.Weighted {
        float total = 0.0f;
        foreach (T obj in arr) total += obj.getWeight();
        float pick = Random.Range (0.0f, total);
        int idx = 0;
        while (idx < arr.Count-1 && arr[idx].getWeight () < pick) pick -= arr[idx++].getWeight();
        return arr[idx];
    }
}