实用小算法合集

1. 获取数组的全排列 ( Permutation )

        public static void FullArrange<T>(List<T> array, int begin, int end, System.Action<System.Collections.ObjectModel.ReadOnlyCollection<T>> call)
        {
            if(begin == end)
            {
                call.Invoke(array.AsReadOnly());
            }
            else
            {
                for(int i = begin; i <= end; i++)
                {
                    Swap(array, begin, i);
                    FullArrange(array, begin + 1, end, call);
                    Swap(array, begin, i);
                }
            }
        }
        private static void Swap<T>(List<T> lsArray, int x, int y)
        {
            var t = lsArray[x];
            lsArray[x] = lsArray[y];
            lsArray[y] = t;
        }

            var list = new List<int>() { 1, 2, 3 };
            FullArrange(list, 0, list.Count - 1, (_array) =>
            {
                string info = "";
                foreach(var data in _array)
                {
                    info += data + ",";
                }
                Debug.Log(info);
            });

 

 

2. 数组的全概率排列 ( 每个位都能选择数组中所有数 )

        public static void Probability<T>(T[] array, int count, System.Action<T[]> call)
        {
            foreach(var data in array)
            {
                Probability(array, 0, count, null, data, call);
            }
        }
        private static void Probability<T>(T[] array, int index, int count, T[] container, T value, System.Action<T[]> call)
        {
            if(container == null)
            {
                container = new T[count];
            }
            container[index] = value;
            if(index == count - 1)
            {
                var newC = new T[count];
                System.Array.Copy(container, newC, count);
                call.Invoke(newC);
            }
            else
            {
                index++;
                foreach(var data in array)
                {
                    var newC = new T[count];
                    System.Array.Copy(container, newC, index);
                    Probability(array, index, count, newC, data, call);
                }
            }
        }

            string[] bb = new string[5] { "+", "-", "x", "/", "%" };
            Probability(bb, 3, (_array) =>
            {
                var str = string.Join(",", _array);
                Debug.Log(str);
            });

 

　　2.1 不需要额外产生数组的版本

        public static void Probability2<T>(T[] array, int count, System.Action<T[]> call)
        {
            var tempArray = new T[count];
            foreach(var data in array)
            {
                Probability2(array, 0, count, tempArray, data, call);
            }
        }
        private static void Probability2<T>(T[] array, int index, int count, T[] container, T value, System.Action<T[]> call)
        {
            if(container == null)
            {
                container = new T[count];
            }
            container[index] = value;
            if(index == count - 1)
            {
                call.Invoke(container);
            }
            else
            {
                index++;
                foreach(var data in array)
                {
                    Probability(array, index, count, container, data, call);
                }
            }
        }

            string[] bb = new string[5] { "+", "-", "x", "/", "%" };
            Probability2(bb, 3, (_array) =>
            {
                var str = string.Join(",", _array);
                Debug.Log(str);
            });

 

 

 

 

 

 

 

 

------------------- Unity3D -------------------

1. 测试渲染是否在相机内的方法, 比系统自带的 OnBecameInvisible 更靠谱, OnBecameInvisible 基本没有用...

    public static bool IsVisible(Renderer renderer, Camera camera)
    {
        Plane[] planes = GeometryUtility.CalculateFrustumPlanes(camera ?? Camera.main);
        return GeometryUtility.TestPlanesAABB(planes, renderer.bounds);
    }