diff --git a/core/src/main/java/com/gitee/drinkjava2/frog/util/Tree4Util.java b/core/src/main/java/com/gitee/drinkjava2/frog/util/Tree4Util.java
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+/* Copyright 2018-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by
+ * applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
+ * OF ANY KIND, either express or implied. See the License for the specific
+ * language governing permissions and limitations under the License.
+ */
+package com.gitee.drinkjava2.frog.util;
+
+import java.util.List;
+
+import com.gitee.drinkjava2.frog.Env;
+
+/**
+ * Tree4Util used to store a pre-order Traversal 4tree array to speed 
+ * 
+ * 这里缓存着一个前序排列的4叉树用来加快速度
+ * 这里的4叉树和4叉树的原理类似，只不过4叉树生成3维形状，4叉树用来生成2维平面形状，对于平面形状生成速度更快
+ * 
+ * 另一种思路是先把基因按绝对值排序，然后顺着多叉树先序排列的次序依次设每个细胞的黑白，可能速度更快且可以很快发现无效和重复基因，但我没时间按这个思路来优化了，以后有时间做。
+ *  
+ * @author Yong Zhu
+ * @since 1.0
+ */
+public class Tree4Util {
+
+    //EIGHT_TREE store a pre-order Traversal tree array  
+    public static final int NODE_QTY = calculateNodeSize(Env.BRAIN_SIZE);
+
+    public static int[][] TREE4 = new int[NODE_QTY][3]; //4叉数用数组表示，第一维是深度树的行号，第二维是一个整数数组,内容是深度树表示的4叉树细胞的size, x, y值
+
+    public static byte[] keep = new byte[NODE_QTY]; //这里临时记录树的敲除记录，大于0的值表示要keep, 小于等于0表示要敲除
+
+    private static byte[] KEEP0 = new byte[NODE_QTY]; //这里保存初值为0的数组常量，可以用System.arraycopy(KEEP, 0, keep, 0, NODE_QTY)快速清空enable数组
+
+    public static int keepNodeQTY = NODE_QTY; //这里临时记录需keep的节点总数，好用来继续敲除，初始值是全部节点
+
+    private static int index = 0;
+    static {
+        tree4Split(0, 0, Env.BRAIN_SIZE);
+    }
+
+    static int calculateNodeSize(int n) {//计算4叉树全展开的总节点数
+        if (n == 1)
+            return 1;
+        return n * n + calculateNodeSize(n / 2);
+    }
+
+    //if cube can split, then split it to 8 small cubes
+    private static void tree4Split(int x, int y, int size) {//如正方形可分裂，就继续递归分裂成4个
+        TREE4[index++] = new int[]{size, x, y}; //这里size类似于深度树中的level，只不过是size从大到小，level是从小到大，原理一样
+        if (size == 1)
+            return;
+        int half = size / 2;//每个细胞可以分裂成4个size为原来1/2的小细胞
+        tree4Split(x, y, half);
+        tree4Split(x + half, y, half);
+        tree4Split(x, y + half, half);
+        tree4Split(x + half, y + half, half);
+    }
+
+    public static void knockNodesByGene(List<Integer> gene) {//根据基因，把要敲除的4叉树节点作敲除或保留标记 
+        System.arraycopy(KEEP0, 0, keep, 0, NODE_QTY);//清空keep数组
+        keepNodeQTY = 0;
+        for (int g : gene) {//g基因，用带符号的4叉数的行号表示，负数表示阴节点要敲除，正数表示是阳节点要保留
+            int gLine = Math.abs(g); //基因对应节点的行号
+            int size = Tree4Util.TREE4[gLine][0]; //size是基因对应节点的细胞正方形边长
+            for (int line = gLine; line < Tree4Util.NODE_QTY; line++) {//从这个g节点开始，往下找节点
+                if (line > gLine && Tree4Util.TREE4[line][0] >= size) //如果除了第一个节点外，边长大于等于size，说明节点不是g的子节点，退出
+                    break;
+                else {//否则就是g的子节点
+                    if (g < 0) { //g是阴节点 
+                        if (Tree4Util.keep[line] == 1) //如果是1，表示这个节点将从保留状态转为删除状态
+                            keepNodeQTY--;
+                        Tree4Util.keep[line] = 0;
+                    } else if (g > 0) { //g是阳节点
+                        if (Tree4Util.keep[line] == 0) //如果是0，表示这个节点将从删除状态转为保留状态
+                            keepNodeQTY++;
+                        Tree4Util.keep[line] = 1;
+                    }
+                }
+            }
+        }
+    }
+
+}