[129] 求根节点到叶节点数字之和

details

遍历所有子路径,把节点转成 number 类型 再求和相加

var sumNumbers = function (root) {
    let path = [];
    dfs('', root);

    function dfs(str, node) {
        if (node === null) return;

        str += node.val;
        if (node.left === null && node.right === null) {
            path.push(str);
        } else {
            dfs(str, node.left);
            dfs(str, node.right);
        }
    }
    return path.reduce((acc, str) => {
        acc += Number(str);
        return acc;
    }, 0);
};

遍历的时候同步相加

var sumNumbers = function (root) {
    return dfs(root, 0);

    function dfs(node, sum) {
        if (node === null) return 0;

        sum = sum * 10 + node.val;
        if (node.left === null && node.right === null) {
            return sum;
        }
        return dfs(node.left, sum) + dfs(node.right, sum);
    }
};