Plane: vertices and triangles

I want to create a plane with n x 1 quads (ex: 10 x 1 quads). I'm able to do so but half of the triangles are showing on one side and the other half on the other side.

First side:

Other side:

How can i make it so all triangles are showing on the same side?

Here is the code i drop on the plane showed above:

 using UnityEngine;
 using System.Collections;
 
 public class test : MonoBehaviour {
     
     public int rectanglesCount = 200;
     
     private Vector3[] _vertices;
     private int[] _triangles;
     
     private Mesh _mesh;
     private Vector3 _size;
     
     void Start ()
     {
         _vertices = new Vector3[(rectanglesCount * 2) + 2];
         _triangles = new int[(rectanglesCount * 6)];
         
         _mesh = ((MeshFilter) GetComponent(typeof(MeshFilter))).mesh;
         _size = collider.bounds.size;
         
         InitiateRectangles();
     }
     
     private void InitiateRectangles()
     {
         _mesh.Clear();
         
         // vertices
         
         /* 
            order
            0 --- 2
            |     |
            |     |
            |     |
            1 --- 3
         */
         
         float xSpace = _size.x / rectanglesCount;
         float x = 0;
         bool top = true;
         
         x -= _size.y / 2;
         
         for(int i = 0; i < _vertices.Length; i++)
         {
             _vertices[i].x = x;
             _vertices[i].z = 0.01f;
             
             if (top)
                 _vertices[i].z = _size.y / 2;
             else
             {
                 _vertices[i].z = - _size.y / 2;
                 
                 x += xSpace;
             }
                 
             top = !top;
         }
         
         top = false;
         
         // triangles
         
         /*
          triangles[0] = 0;
         _triangles[1] = 1;
         _triangles[2] = 2;
         
         _triangles[3] = 1;
         _triangles[4] = 2;
         _triangles[5] = 3;
         
         _triangles[6] = 2;
         _triangles[7] = 3;
         _triangles[8] = 4;
         */
         
         int index = 0;
         
         for(int i = 0; i < (_triangles.Length / 3); i ++)
         {
             index = i * 3;
             
             _triangles[index] = i;
             _triangles[index + 1] = i + 1;
             _triangles[index + 2] = i + 2;
         }
         
         _mesh.vertices = _vertices;
         _mesh.triangles = _triangles;
         
         _mesh.RecalculateNormals();
         _mesh.RecalculateBounds();
     }
 }