1372 二叉树中的最长交错路径

code

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var longestZigZag = function(root) {
    let max = 0;
    function traverse(root, direction, accumulate){
        if(root === null){
            return;
        }
        max = Math.max(max, accumulate);

        if(direction === -1){
            traverse(root.left, -1, 1);
            traverse(root.right, 1, accumulate + 1);
        }
        if(direction === 1){
            traverse(root.left, -1, accumulate + 1);
            traverse(root.right, 1, 1);
        }
    }
    traverse(root.left, -1, 1);
    traverse(root.right, 1, 1);
    return max; 
};

总结

1. 说到底这类我感觉都没啥难的，携带着每一层的状态然后提公共的即可