572. Subtree of Another Tree

Problem: Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.

给两个树，判断t是不是s的子树。

解决思路：依次遍历s的TreeNode，判断是不是跟t完全一样。

class Solution {
public:
    bool isSame(TreeNode* s, TreeNode* t) {
        if(s==nullptr && t==nullptr)
            return true;
        else if(s && t) {
            if(s->val == t->val)
                return (isSame(s->left, t->left) && isSame(s->right, t->right));
            return false;
        }
        else
            return false;
    }
    bool isSubtree(TreeNode* s, TreeNode* t) {
        if(s) {
            if(isSame(s, t))
                return true;
            return (isSubtree(s->left, t) || isSubtree(s->right, t));  
        }
        return false;
    }
};