Unity C# 优先队列

实现了支持泛型的优先队列,解决Unity官方不提供优先队列的问题。

API

属性和字段 解释
size 队列的长度
capacity 队列的容量
IsEmpty 返回队列是否为空
Top 返回队列第一个元素
枚举 解释
PriorityQueueMode.less 最小优先队列
PriorityQueueMode.equal 只会将相等的排在一起
PriorityQueueMode.greator 最大优先队列
函数 功能
Push 入队一个元素
Pop 出队一个元素
Peek 返回第一个元素
Clear 清空队列

示例

PriorityQueue<int> priorityQueue = new PriorityQueue<int>((a, b) => {
            if (a < b) return -1;
            else if (a == b) return 0;
            else if (a > b) return 1;
            return 0;
});

priorityQueue.Push(8);
priorityQueue.Push(9);
priorityQueue.Push(3);
priorityQueue.Push(2);
priorityQueue.Push(7);
priorityQueue.Push(5);
priorityQueue.Push(0);

while (!priorityQueue.IsEmpty) {
    Debug.Log(priorityQueue.Top);
    priorityQueue.Pop();
}

实现

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System;

namespace YBZ.Algorithm {
    public class PriorityQueue<T> where T : new ()
    {
        public int size;
        public int capacity;
        private T[] elements;

        // 是否为空
        public bool IsEmpty { get => size == 0; }

        /// 返回顶部元素
        public T Top { get => elements[0]; }

        /// 优先队列的模式
        private PriorityQueueMode _comparator;

        public enum PriorityQueueMode {
            less = -1, // 最小优先队列
            equal = 0, // 相等的排在一起
            greater = 1 // 最大优先队列
        }

        /// 
        /// 以CMP(a,b) 为例:
        /// 当a>b时,返回1,表示放右边
        /// 当a==b时,返回0,表示不变
        ///  当a
        /// 
        private Func<T,T,int> CMP;
        
        /// 
        /// 构造函数, 必须实现
        /// 
        /// 
        /// 
        /// 
        public PriorityQueue(Func<T,T,int> CMP, PriorityQueueMode priorityQueueMode = PriorityQueueMode.less, int capacity = 1) {
            this.CMP = CMP;
            this.size = 0; // 数组索引从0开始
            this.capacity = capacity;
            this.elements = new T[capacity];
            this._comparator = priorityQueueMode;
        }

        /// 
        /// 入队
        /// 
        /// 
        public void Push(T value) {
            if (size == capacity) {
                ExpandCapacity();
            }
            elements[size++] = value;

            ShiftUp();
        }

        /// 
        /// 出队
        /// 
        public void Pop() {
            if(size == 0) {
                return;
            }
            size--;
            Swap(ref elements[0], ref elements[size]);

            ShiftDown();
        }

        /// 
        /// 清空队列
        /// 
        public void Clear() {
            size = 0;
        }

        /// 
        /// 返回位于Queue开始处的对象但不将其移除。
        /// 
        /// 返回第一个队列中元素
        public T Peek() {
            return Top;
        }

        /// 
        /// 扩展队列的容量
        /// 
        private void ExpandCapacity() {
            capacity = Mathf.CeilToInt(capacity * 1.5f);
            T[] temp = new T[capacity];

            for (int i = 0; i < elements.Length; i++) {
                temp[i] = elements[i];
            }
            elements = temp;
        }
        
        // 从下到上 重排序 
        private void ShiftUp() {
            int cur = size - 1 ;
            int parent = ( cur -1 ) >> 2;
            while (cur > 0) 
            {
                if (CMP(elements[cur],elements[parent]) == (int)_comparator) {
                    Swap(ref elements[cur], ref elements[parent]);
                    cur = parent;
                    parent = (cur - 1) >> 2;
                } else break;
            }
        }

        // 从上到下 重排序
        private void ShiftDown() {
            int cur = 0;
            int child = 1;
            while (child < size) {
                if (child + 1 < size && CMP(elements[child +1], elements[child]) == (int)_comparator) {
                    child++;
                }

                if (CMP(elements[child], elements[cur]) == (int)_comparator){

                    Swap(ref elements[child], ref elements[cur]);
                    cur = child;
                    child = cur << 1 + 1;
                } else break;
            }
        }

        /// 
        /// 交换传入的两个元素
        /// 
        /// 
        /// 
        private void Swap(ref T lhs,ref T rhs) {
            T temp = lhs;
            lhs = rhs;
            rhs = temp;
        }

        /// 
        /// 返回队列中的所有元素,对于ToString()函数,值类型会返回值,引用类型会返回数据类型
        /// 
        /// 
        public override string ToString() {
            string result = "";
            foreach (var v in elements) {
                result += v.ToString();
            }
            return result;
        }
    }
}

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