Find nearest waypoint to target in unity 3d - unity3d

Question

I'm developing game like Hitman Go , and I need to find which waypoints are closest to my target(specific waypoint ) when enemy has alerted by rock or sound and etc.
I set some point for enemy and My enemy patrolling between waypoints ( 8 -> 6 -> 1-> 2-> 3-> 4-> 5 ) then reveres his path.
so, when I throw rock in waypoint number 18, I need to move enemy to this waypoint, but with closest way. imaging enemy can be any this waypoint when he get aleret ( 8,6,1,2,3,4,5 points).
Note 1: The distance between two points is same.
Note2: My game is in 3d not 2d.
I use this code to move my enemy step by step ( turn base ).
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class WaypointController : MonoBehaviour
{
public List<Transform> waypoints = new List<Transform>();
private Transform targetWaypoint;
private int targetWaypointIndex = 0;
private float minDistance = 0.1f;
private int lastWaypointIndex;
public bool reversePath;
// what easetype to use for iTweening
public iTween.EaseType easeType = iTween.EaseType.easeInOutExpo;
// how fast we move
public float moveSpeed = 1.5f;
// time to rotate to face destination
public float rotateTime = 0.5f;
// delay to use before any call to iTween
public float iTweenDelay = 0f;
// Use this for initialization
void Start()
{
lastWaypointIndex = waypoints.Count - 1;
targetWaypoint = waypoints[targetWaypointIndex];
}
public void EnemyTurn()
{
float distance = Vector3.Distance(transform.position, targetWaypoint.position);
CheckDistanceToWaypoint(distance);
// move toward the destinationPos using the easeType and moveSpeed variables
iTween.MoveTo(gameObject, iTween.Hash(
"x", targetWaypoint.position.x,
"y", targetWaypoint.position.y,
"z", targetWaypoint.position.z,
"delay", iTweenDelay,
"easetype", easeType,
"speed", moveSpeed
));
}
void CheckDistanceToWaypoint(float currentDistance)
{
if (currentDistance <= minDistance)
{
targetWaypointIndex++;
UpdateTargetWaypoint();
}
}
void UpdateTargetWaypoint()
{
if (targetWaypointIndex > lastWaypointIndex)
{
if (reversePath)
{
waypoints.Reverse();
}
targetWaypointIndex = 1;
}
targetWaypoint = waypoints[targetWaypointIndex];
}
}

Answer 1

Since you asked in the comments for a non-A* solution & I was bored :)
Naive DFS pathfinder with very simple pruning.
Brute force and very wasteful both memory & CPU wise.
For a game similar to Hitman Go / Lara Croft Go - I would use this code and not a navmesh / A*.
For a RTS / FPS or any AI intensive games, I would definitely not use this solution.
public class GridPathfinder
{
// Not thread safe
private int? _currentShortestPath;
/// <summary>
/// Finds shortest path from cell A to B
/// </summary>
/// <returns>Shortest found path; null if found no path.</returns>
public IList<Node> GetShortestPath(Node a, Node b)
{
_currentShortestPath = null;
return GetShortestPathInternal(a, b, new List<Node>());
}
private IList<Node> GetShortestPathInternal(Node #from, Node to, List<Node> currentPath)
{
// Sanity
if (currentPath.Contains(from))
{
return null;
}
// Prune
if (_currentShortestPath.HasValue && currentPath.Count + 1 >= _currentShortestPath)
{
return null;
}
currentPath.Add(from);
if (from == to)
{
return currentPath;
}
// Check neighbors recursively
IList<Node> foundShortestPath = null;
foreach (var connectedCell in from.ConnectedCells)
{
var cellPath = GetShortestPathInternal(connectedCell, to, new List<Node>(currentPath));
if (cellPath == null || foundShortestPath != null && cellPath.Count >= foundShortestPath.Count)
{
continue;
}
foundShortestPath = cellPath;
}
// Update shortest path for future pruning
if (foundShortestPath != null && (!_currentShortestPath.HasValue || _currentShortestPath > foundShortestPath.Count))
{
_currentShortestPath = foundShortestPath.Count;
}
return foundShortestPath;
}
}
public class Node
{
private readonly HashSet<Node> _connectedCells = new HashSet<Node>();
public IEnumerable<Node> ConnectedCells => _connectedCells;
/// <summary>
/// Add a connection
/// </summary>
/// <param name="toAdd">Node to add</param>
/// <param name="isTwoWay">Should add a connection from target node to this node</param>
public void AddConnection(Node toAdd, bool isTwoWay=true)
{
if (toAdd == null || toAdd == this)
{
throw new Exception("Invalid connection attempted");
}
// Attempt to add
if (!_connectedCells.Add(toAdd))
{
return;
}
if (!isTwoWay) return;
toAdd.AddConnection(this);
}
}