pick a random int with the value of 1 from an array

Question

I have this script that sets all the int in the 12 int long array to 0:

 int[] songs = new int [12];
     // Use this for initialization
     void Start () {
         
         for(int i=0; i<songs.Length; i++){
             songs [i] = 1;
             Debug.Log(songs [i]);
         }
         Set ();
     }

how do I set a int to a ranomd int from the array that has the value of 1 (int his cause it would choose from all of them cause they're all set to 1) something like this:

  int random_pick = random number from songs that is = to 1

for eg. it would pick the 3rd int and the int random_pick would be equal to 3. thanks for your help in advanced.

Answer 1

Answer by sleepandpancakes · Apr 04, 2017 at 05:09 AM

If I understand correctly, you want to find all the indices where which the array element is equal to 1, then pick a random index from those indices. This code is untested but I think it should get you what you need.

 void GetRandomElementWithValue(int value)
 {
     int[] indices = Array.FindAll(sounds, x => x == value);
     int randomIndex = indices[Random.Range(0, indices.Length)];
 }

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NoseKills · Apr 04, 2017 at 03:57 PM 1

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I suspect this doesn't work as intended. FindAll() returns an array with all the elements in the source array that fulfill the predicate (not the indices of those elements) -> it'll be an array with as many 1s as there were in the source array.

If the source array has only one "1" left at let's say index 5 indices will be an array with one "1", and randomIndex will become that 1.

sleepandpancakes NoseKills · Apr 04, 2017 at 04:34 PM 0

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Oh right, I forgot about that. In that case, @banana111, you could either just make a List for the indices and iterate through the array, or you could use the method to get an array of all the indices as described in this page.

Answer 2

Store the index of the songs that meet your criteria in a list. Then, select an random item from that list.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using System.Linq;
 
 public class RandomSong : MonoBehaviour {
 
     int[] songs = new int[12];
 
     void Start()
     {
         for (int i = 0; i < songs.Length; i++)
         {
             songs[i] = 0; // I turned all to 0 for this example.
         }
 
         songs[9] = songs[11] = 1; // Then, I turned only these to 1.
 
         int random_pick = 0;
         if (songs.Any(x => x == 1)) // Make sure at least one song = 1.
             random_pick = GetRandomSongWithValue(1);
 
         Debug.Log(random_pick); // This will be either 9 or 11.
     }
 
     int GetRandomSongWithValue(int value)
     {
         // Make a list of the indecise of all songs with a value of 1.
         List<int> usableIndecise = new List<int>();
         for (int i = 0; i < songs.Length; i++)
         {
             if (songs[i] == value)
                 usableIndecise.Add(i);
         }
 
         // Return a random index.
         return usableIndecise[UnityEngine.Random.Range(0, usableIndecise.Count)];
     }
 }

pick a random int with the value of 1 from an array

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