image.png

image.png

解法

/**
 * 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 {
    public boolean isSubStructure(TreeNode A, TreeNode B) {
        if (A != null && B != null) {
            // 挨个去试，简化为比较以A的当前节点比较两者是否重合
            return recur(A, B) || isSubStructure(A.left, B) 
            || isSubStructure(A.right, B); 
        } else {
            return false;
        }
    }

    private boolean recur(TreeNode A, TreeNode B) {
        if (B == null) {
            return true;
        }
        if (A == null || A.val != B.val) {
            return false;
        }
        return recur(A.left, B.left) && recur(A.right, B.right);
    }
}