[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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Hide Similar Problems (M) Count Complete Tree Nodes (H) Closest Binary Search Tree Value II

BST的題,大部分都是recursion。並且這道題只有一個answer。 難度確實是easy。所以iterative也超級簡單。

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;
    }
};

recursion:

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;
        }
    }
};
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