先盘对两个数是不是一样的树，不是的话去看是不是和s->left,s->right一样的树。
bool isSametree(struct TreeNode* s, struct TreeNode* t) {
if(s == NULL && t == NULL) return true;
if(s == NULL || t == NULL) return false;
if(s->val != t->val) return false;
return isSametree(s->left,t->left) && isSametree(s->right, t->right);
}
bool isSubtree(struct TreeNode* s, struct TreeNode* t) {
if(s == NULL)
return false;
if(isSametree(s,t))
return true;
return isSubtree(s->left,t) || isSubtree(s->right,t);
}
···