[LeetCode270]Closest Binary Search Tree Value

Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target.

Note:
Given target value is a floating point.
You are guaranteed to have only one unique value in the BST that is closest to the target.
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class Solution {
public:
int closestValue(TreeNode* root, double target) {
int closest = root->val;
if(!root->left && !root->right) return root->val;
while(root){
if(abs(root->val - target) <= abs(closest - target)){
closest = root->val;
}
if(target <= root->val) root = root->left;
else root = root->right;
}
return closest;
}
};

class Solution {
public:
int closestValue(TreeNode* root, double target) {
int a = root->val;
TreeNode* node = (target < a) ? root->left : root->right;
if(!node) return a;
int b = closestValue(node, target);
return (abs(a-target) < abs(b-target)) ? a : b;
}
}
};