程式語言 - LeetCode - C - 1372. Longest ZigZag Path in a Binary Tree

參考資訊：
https://www.cnblogs.com/cnoodle/p/17342376.html

題目：


解答：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
int max(int a, int b)
{
    return a > b ? a : b;
}

int dfs(struct TreeNode *n, int cnt, int left)
{
    int r = 0;

    if (!n) {
        return cnt;
    }

    if (left) {
        if (n->left) {
            r = max(dfs(n->left, cnt + 1, 0), r);
        }

        if (n->right) {
            r = max(dfs(n->right, 1, 1), r);
        }
    }
    else {
        if (n->right) {
            r = max(dfs(n->right, cnt + 1, 1), r);
        }

        if (n->left) {
            r = max(dfs(n->left, 1, 0), r);
        }
    }

    return max(cnt, r);
}

int longestZigZag(struct TreeNode* root)
{
    return dfs(root, 0, 0);
}