RandomPlatforms.cs

using UnityEngine;
using System.Collections;

public class RandomPlatforms : MonoBehaviour {
    GameObject platform;
    GameObject enemy;
    int numPlatforms, ranIndex, numEnemies;
    double[] heights = {-1.39, 1, 4.11,  6.32, 8.57 };

	// Use this for initialization
	void Start () {
        platform = GameObject.Find("platform");
        numPlatforms = Random.Range(30, 60);
        enemy = GameObject.Find("Enemy");
        numEnemies = Random.Range(2, 5);
        for(int i = 0; i < numPlatforms; i++) { 
            ranIndex = Random.Range(0, 5);
            GameObject platformapus = Instantiate(platform, new Vector3( Random.Range(-20, 67 ), (float)heights[ranIndex], 10), Quaternion.identity) as GameObject;
        }
        for (int i = 0; i < numEnemies; i++)
        {
            ranIndex = Random.Range(0, 5);
            GameObject enenemenenies = Instantiate(enemy, new Vector2(Random.Range(-10, 124), (float)heights[ranIndex]), Quaternion.identity) as GameObject;
        }

 	}
}