Question: Weird behaviour with max in C++

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I was trying out a problem (irrelevant) on LeetCode — 1372. Longest ZigZag Path in a Binary Tree. I posted this question on the forum but got no reply. Hence, I am asking the same question here.

I noticed some weird behaviour when using the max function. I took a max in two ways:

Solution 1: max(1 + a, 1 + b)

Solution 2: 1 + max(a, b)

Both of these do exactly the same task of getting the 1 + max. However:

Solution 1: — Runtime Error!
Solution 2: — Accepted

The full code is also given below:

Solution 1

class Solution {
public:
    int longestZigZag(TreeNode* root) {
        return zigzag(root)[2];
    }
    
    vector<int> zigzag(TreeNode* node) {
        if(!node)
            return {-1, -1, -1};
        vector<int> left, right;
        left = zigzag(node->left);
        right = zigzag(node->right);
        int h = max(max(1 + left[1], 1 + right[0]), max(left[2], right[2]));
        return {1 + left[1], 1 + right[0], h};
    }
};

Solution 2

class Solution {
public:
    int longestZigZag(TreeNode* root) {
        return zigzag(root)[2];
    }
    
    vector<int> zigzag(TreeNode* node) {
        if(!node)
            return {-1, -1, -1};
        vector<int> left, right;
        left = zigzag(node->left);
        right = zigzag(node->right);
        int h = max(1 + max(left[1], right[0]), max(left[2], right[2]));
        return {1 + left[1], 1 + right[0], h};
    }
};

The details for Solution 1 are given below:

Runtime Error Message: AddressSanitizer: stack-overflow on address 0x7ffee1685ab8 (pc 0x7f4840414c34 bp 0x7ffee1686300 sp 0x7ffee1685aa0 T0)
Failed Input

If you notice, the code for both of them is exactly the same except for line 13. Could someone please tell me why Solution 1 fails? It really makes no sense to me.

Thank you for all your help!

	Rev.	Lang.	By	When	Δ	Comment
	en2		Mohammed-Shoaib	2020-03-11 05:37:23	12
	en1		Mohammed-Shoaib	2020-03-11 05:36:37	2437	Initial revision (published)

Rev.

Lang.

When

Comment

en2

Mohammed-Shoaib

2020-03-11 05:37:23

en1

Mohammed-Shoaib

2020-03-11 05:36:37

2437

Initial revision (published)

History