leetcode Day4

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从零开始Leetcode – Day 4

LeetCode总结 – 树的性质篇
http://blog.csdn.net/linhuanmars/article/details/39024195
这个博客分析得不错。

总结一下今天：

  1. 前一天晚上要休息好， 才有可能下班后再刷题.
  2. 效率要提高。 不要花太多时间去摸索， 想不出来直接网上看代码， 转换成javascript.

Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.
https://leetcode.com/problems/binary-tree-paths/

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var binaryTreePaths = function(root) {
    if (!root) {
        return [];
    }
    var str = "";
    var results = [];

    helper(str, results, root);
    return results;
};

var helper = function(str, results, node) {
    if (!node) {
        return;
    }

    if (node.left) {
        var leftStr = str + node.val + "->";
        helper(leftStr, results, node.left);
    }

    if (node.right) {
        var rightStr = str + node.val + "->";
        helper(rightStr, results, node.right);
    }

    if (!node.left && !node.right) {
        var path = str + node.val;
        results.push(path);
    }
};