572. 另一棵樹的子樹

解題思路

• 遍歷二叉樹的思路
• 針對每一個節(jié)點(diǎn)判斷該節(jié)點(diǎn)的子樹和subtree是不是相等
• 需要編寫判斷兩個子樹是否相等的函數(shù)

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {// 比較兩個樹是不是相等public boolean isSame(TreeNode root,TreeNode root1){// 二叉樹的遍歷問題  針對當(dāng)前節(jié)點(diǎn)  寫出所有遞歸出口if(root == null && root1 == null){return true;}if(root == null || root1 == null){return false;}if(root.val != root1.val){return false;}return isSame(root.left,root1.left) && isSame(root.right,root1.right);}public boolean isSubtree(TreeNode root, TreeNode subRoot) {// 二叉樹的遍歷問題  針對二叉樹每一個點(diǎn)繼續(xù)遍歷  模板題// 對于遍歷到的每一個節(jié)點(diǎn)  也就是先寫出遞歸出口if(root == null){return subRoot == null;}if(isSame(root,subRoot)){return true;}// 從左右子樹開始繼續(xù)尋找是否有相同的子樹return isSubtree(root.left,subRoot) || isSubtree(root.right,subRoot);}
}