Java Extremely Simple to understand - Short Code - Recursion

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    Every time we pass to the left child of a tree, we pass in True. Every time we pass right, we pass in False.

    When it finally gets to a leaf node, the receive a True if it is a left leaf.

    public class Solution {
        public int sumOfLeftLeaves(TreeNode root) {
            return recur(root, false);
        public int recur(TreeNode current, boolean left) {
            if(current == null) return 0;
            if(current.left == null && current.right == null && left) return current.val;
            int count = 0;
            count += recur(current.left, true);
            count += recur(current.right, false);
            return count;

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