Moving objects on Mouse swipe is a very interesting way of getting user input , it is very different from traditional approach of getting input from keyboard keys . It provids user with unique experience and makes user part of the game.

Below is the code for getting Mouse swipe in Left , Right , Up , Down direction .

using UnityEngine;
using System.Collections;

public class PlayerMove : MonoBehaviour 
{
    private Vector2 initialPos ;
   void Update () 
    {
        if( Input.GetMouseButtonDown(0) )
        {
            initialPos = Input.mousePosition;
        }

        if( Input.GetMouseButtonUp(0))
        {       
            Calculate(Input.mousePosition);
        }

    }

void Calculate(Vector3 finalPos)
    {
        float disX = Mathf.Abs(initialPos.x - finalPos.x);

        float disY = Mathf.Abs(initialPos.y - finalPos.y);

        if(disX>0 || disY>0)
        {
                if (disX > disY) 
                {
                    if (initialPos.x > finalPos.x)
                    {
                        Debug.Log("Left");
                    }
                    else
                    {
                        Debug.Log("Right");
                    }
                }
                else 
                {   
                    if (initialPos.y > finalPos.y )
                    {
                       Debug.Log("Down");
                    }
                    else
                    {
                        Debug.Log("Up");
                    }
                }
        }
    }

}