一个树是否包含了另一个树

src/Question26.java

@@ -0,0 +1,66 @@
+public class Question26 {
+    private static boolean findRoot = false;
+    public static void main(String[] args) {
+        TreeNode father = new TreeNode(1);
+        TreeNode node1 = new TreeNode(2);
+        TreeNode node2 = new TreeNode(3);
+        TreeNode node3 = new TreeNode(4);
+        TreeNode node4 = new TreeNode(5);
+        TreeNode node7 = new TreeNode(2);
+
+        father.left = node1;
+        father.right = node2;
+        node1.left = node7;
+        node7.left = node3;
+        node7.right = node4;
+
+        TreeNode child = new TreeNode(2);
+        TreeNode node5 = new TreeNode(4);
+        TreeNode node6 = new TreeNode(5);
+        child.left = node5;
+        child.right = node6;
+
+        System.out.println(containChildTree(father, child));
+    }
+
+    static boolean containChildTree(TreeNode father, TreeNode child){
+        //规定null可以是任何树的子树
+        if (child == null){
+            return true;
+        }
+        //father树遍历到叶子节点也没找到和child根节点相同的节点，那该分支返回false
+        if (father == null){
+            return false;
+        }
+        //father树遍历过程中找到了节点和child根节点相同节点，从该节点开始和child树一起向下遍历看是否能包含child树。
+        //同时不能忘了此时可能只是当前节点等于了child根节点，那要把该节点下面的子树的包含情况也带上
+        if (father.value == child.value){
+            return loopChild(father, child) || containChildTree(father.left, child) || containChildTree(father.right, child);
+        }
+        //一直向下遍历找到起始节点
+        return containChildTree(father.left, child) || containChildTree(father.right, child);
+    }
+
+    static boolean loopChild(TreeNode father, TreeNode child){
+        //child遍历到其中一个叶子过程中都与father树节点相同，该分支可以返回true了
+        if (child == null){
+            return true;
+        }
+        //当有节点值不等时返回false
+        if (father == null || father.value != child.value){
+            return false;
+        }
+        //遍历左右2个分支一直到child所有的叶子，将结果并起来为最终结果
+        return loopChild(father.left, child.left) && loopChild(father.right, child.right);
+    }
+
+    static class TreeNode{
+        int value;
+        TreeNode left;
+        TreeNode right;
+
+        public TreeNode(int value) {
+            this.value = value;
+        }
+    }
+}