[98] Validate Binary Search Tree

其實我真的不會寫扣吧......

就算安慰自己這是暖身題, 還是覺得.......嗯....

好吧我不說了 XD

/**

 * Definition for a binary tree node.

 * struct TreeNode {

 *     int val;

 *     struct TreeNode *left;

 *     struct TreeNode *right;

 * };

 */

bool valid(struct TreeNode* node, long min, long max)

{

    if (node== NULL)

        return true;

    int val= node->val;

    if ((val <= min) || (val >= max))

        return false;

    return (valid(node->left , min, val) && valid(node->right,val,max));

}

bool isValidBST(struct TreeNode* root){

    return valid(root, -2147483649, 2147483648);

}