algorithm/Week_02/id_119/LeetCode_671_119.cpp at master · feixiangcode/algorithm · GitHub

26 lines (25 loc) · 722 Bytes

/**

* Definition for a binary tree node.

* struct TreeNode {

* int val;

* TreeNode *left;

* TreeNode *right;

* TreeNode(int x) : val(x), left(NULL), right(NULL) {}

* };

class Solution {

public:

int findSecondMinimumValue(TreeNode* root) {

long first = root->val, second = LONG_MAX;

helper(root, first, second);

return (first == second || second == LONG_MAX) ? -1 : second;

}

void helper(TreeNode* node, long &first, long &second) {

if (!node) return;

if (node->val != first && node->val < second) {

second = node->val;

}

helper(node->left, first, second);

helper(node->right, first, second);

}

};

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