Leetcode 45 - Jump game II - greedy algorithm

Leetcode45_JumpGameII_greedy.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace JumpGameII
{
    class JumpGameII
    {
        static void Main(string[] args)
        {
            RunTestcase();
        }

        public static void RunTestcase()
        {
            var testcase = new int[] { 2, 3, 1, 1, 4 };

            var numberSteps = Jump_backwardGreedy(testcase);
        }       

        /// <summary>
        /// June 23, 2017
        /// Code review please!
        /// 
        /// Start from last index. For each step, find the smallest index 
        /// it can jump from and then update the last index until last index reaches zero.
        /// The greedy algorithm works, how come? Figure out
        /// Backward algorithm 
        /// </summary>
        /// <param name="nums"></param>
        /// <returns></returns>
        public static int Jump_backwardGreedy(int[] nums)
        {
            int lastIndex = nums.Length - 1;
            int step = 0;
            int smallestIndex;

            while (lastIndex != 0)
            {
                // find smallest index to reach 
                for (smallestIndex = 0; smallestIndex < lastIndex; smallestIndex++)
                {
                    var current = nums[smallestIndex];

                    if (smallestIndex + current >= lastIndex)
                    {
                        break;
                    }
                }

                if (smallestIndex == lastIndex)
                {
                    return -1;
                }

                lastIndex = smallestIndex;
                step++;
            }

            return step;
        }        
    }
}