力扣：1022. 从根到叶的二进制数之和

package com.算法专练.力扣.从根到叶的二进制数之和;

import java.util.ArrayList;
import java.util.List;


public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        TreeNode root = new TreeNode(1, new TreeNode(0, new TreeNode(0), new TreeNode(1)),
                new TreeNode(1, new TreeNode(0), new TreeNode(1)));
        System.out.println(solution.sumRootToLeaf(root));
    }

    public int sumRootToLeaf(TreeNode root) {
        int ans = 0;
        if (root == null){
            return ans;
        }
        List list = new ArrayList<>();
        dfs(root, "", list);
        for (String str : list){
            ans += binaryToTen(str);
        }
        return ans;
    }

    
    private int binaryToTen(String binary){
        int length = binary.length() - 1, i = 0;
        int result = 0;
        while (i <= length){
            result += (binary.charAt(i) -'0') << (length - i++);
        }
        return result;
    }

    
    private void dfs(TreeNode node, String str, List list){
        if (node.left != null){
            dfs(node.left, str + node.val, list);
        }

        if (node.left == null && node.right == null){
            list.add(str + node.val);
        }

        if (node.right != null){
            dfs(node.right, str + node.val, list);
        }
    }

}

class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode() {}
      TreeNode(int val) { this.val = val; }
      TreeNode(int val, TreeNode left, TreeNode right) {
          this.val = val;
          this.left = left;
          this.right = right;
      }
}