剑指offer：树的子结构

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    bool issubtree(TreeNode* p1, TreeNode* p2){
        if(p2 == nullptr) return true;
        if(p1 == nullptr) return false;
        if(p1 -> val == p2 -> val){
            return issubtree(p1 -> left, p2 -> left)
                && issubtree(p1 -> right, p2 -> right);
        }else
        return false;
    }
    bool HasSubtree(TreeNode* pRoot1, TreeNode* pRoot2)
    {
        if(pRoot2 == nullptr || pRoot1 == nullptr) return false;
        return HasSubtree(pRoot1 -> left, pRoot2) || HasSubtree(pRoot1 -> right, pRoot2)
            || issubtree(pRoot1, pRoot2);
    }
};