OJ1 Two Sum

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

TwoSum for sorted array. TwoSum2 for non-sorted array.

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

namespace TwoSum
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] numbers = { 2, 7, 11, 15 };
            int target = 9;
            TwoSum2(numbers, target);
        }

        public static int[] TwoSum(int[] numbers, int target)
        {
            int[] result = new int[2];
            int start = 0;
            int end = numbers.Length - 1;
            while (start < end)
            {
                if (numbers[start] + numbers[end] == target)
                {
                    result[0] = start + 1;
                    result[1] = end + 1;
                    break;
                }
                if (numbers[start] + numbers[end] < target)
                {
                    start++;
                }
                else
                {
                    end--;
                }
            }
            if (result[0] == 0 && result[1] == 0)
            {
                throw new Exception("Didn't find result");
            }
            else
            {
                Console.WriteLine("index1=" + result[0] + ", index2=" + result[1]);
                return result;
            }
        }

        public static int[] TwoSum2(int[] numbers, int target)
        {
            int[] results = new int[2];
            Hashtable ht = new Hashtable();
            for (int i = 0; i < numbers.Length; i++)
            {
                ht.Add(numbers[i],i);
            }
            for (int i = 0; i < numbers.Length; i++)
            {
                if (ht[target - numbers[i]]!=null && (int)ht[target - numbers[i]]!=i)
                {
                    results[0] = i +1;
                    results[1] = (int)ht[target - numbers[i]] + 1;
                    break;
                }
            }
            if (results[0] == 0 && results[1] == 0)
            {
                throw new Exception("Didn't find result");
            }
            else
            {
                Console.WriteLine("index1=" + results[0] + ", index2=" + results[1]);
                return results;
            }
        }
    }
}