Leetcode Daily Challenge Solutions

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Today's 14-04-24

404. Sum of Left Leaves

Intuition

The goal is to find the sum of all left leaves in a binary tree. A left leaf is a leaf node that is the left child of its parent.

Approach

• I started with the root node.
• If the current node is null, returned 0.
• Check if the left child of the current node exists and if it is a leaf node (i.e., it has no left or right children).
• If the left child is a leaf node, add its value to the result and continue recursively with the right child.
• If the left child is not a leaf node, recursively call the function on both the left and right children.
• Returned the sum obtained from the left subtree and the right subtree.

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Have a look at the code , still have any confusion then please let me know in the comments Keep Solving.:)

Complexity

• Time complexity : $O(n)$

$n$ : number of nodes in the binary tree

• Space complexity : $O(n)$

Code

/**
 * Definition for a binary tree node.
 * public 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;
 *     }
 * }
 */

class Solution {
    public int sumOfLeftLeaves(TreeNode root) {
        if (root == null) {
            return 0;
        }
		
		// Checking if the left node is a leaf node
        if (root.left != null && root.left.left == null && root.left.right == null) {
            return root.left.val + sumOfLeftLeaves(root.right);
        }

		// Exploring the tree further
        return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
    }
}