Western Tech Interview Prep Session #3

sumRootToLeaf.java

public class Solution {
    public int sumNumbers(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int sum = 0;
        return dfs(root,sum);
    }
    
    public int dfs(TreeNode root, int sum) {
        if (root == null) return 0;
        if (root.left == null && root.right == null)  {
            //System.out.println(sum);
            return concatIntStr(root.val,sum);
        }
        
        sum = concatIntStr(root.val,sum);
        //System.out.println(sum);
        return dfs(root.left, sum) + dfs(root.right, sum);
    }
    
    public int concatIntStr(int rootVal, int sum) {
        String sumStr = Integer.toString(sum);
        String rootValStr = Integer.toString(rootVal);
        sumStr = sumStr + rootValStr;
        sum = Integer.parseInt(sumStr);
        return sum;
    }
}