[Algorithm] 48 week(12.26 ~ 12.31) 3/3

687. Longest Univalue Path

var longestUnivaluePath = function(root) {
    if(!root) return 0;

    const dfs = (node, val) => {
        if(!node || node.val !== val) return 0;

        const left = dfs(node.left, val);
        const right = dfs(node.right, val);

        return 1 + Math.max(left, right);
    }

    return Math.max(dfs(root.left, root.val) + dfs(root.right, root.val), longestUnivaluePath(root.left), longestUnivaluePath(root.right))
};