Given an array of integers, return indices of the two numbers such that they add up to a specific target.

TwoSum.cs

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        
        //Get length of the array
        int len = nums.Length;
        
        //Create a dictionary of array elements
        var map = new Dictionary<int,int>();
        for(int i=0;i<len;i++){
            if(map.ContainsKey(nums[i])){
                map[nums[i]] = map[nums[i]]+1;
            }
            else{
                map.Add(nums[i],1);
            }
        }
        
        //Array to store output
        int[] index = new int[2];
        bool found = false;
        int num = 0;
        
        for(int i=0;i<len;i++){
            num = target-nums[i];
            if(map.ContainsKey(num)){
                if( (num == nums[i]) && map[nums[i]]>=2 ){
                        index[0] = i;
                        found = true;
                        break;
                }
                else if(num != nums[i]){
                        index[0] = i;
                        found = true;
                        break;
                }
                
            }
        }
        
        if(found){
            for(int i=0;i<len;i++){
                if(i!=index[0] && nums[i] == num){
                    index[1] = i;
                    break;
                }
            }
            
            return index;
        }
        
        return new int[0];
        
    }
}