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Problem Statement

You have given a binary tree, find out the sum of all left leaves value.

Example 

There are two left leaves in above binary tree, 9 and 15, So result should be 24.

Algorithm 

We can use Depth First Traversal algorithm to solve this problem.

Program 

public class DFS {

	public static void main(String[] args) {
		
		DFS dfs = new DFS();
		
		TreeNode root = new TreeNode(3);
		root.left = new TreeNode(9);
		root.right = new TreeNode(20);		
		root.right.left = new TreeNode(15);
		root.right.right = new TreeNode(7);
		
		int result = dfs.sumOfAllLeftLeaves(root);
		System.out.println(result);
	}
	
	public int sumOfAllLeftLeaves(TreeNode root) {
        return dfs(root, false, 0);
    }

	public int dfs(TreeNode node, boolean isLeft, int sum){
        
        if(node == null) {
        	return sum;
        }
        
        if(node.left == null && node.right == null && isLeft){
            sum = sum + node.val;
            return sum;
        }
        
        sum = dfs(node.left, true, sum);
        sum = dfs(node.right, false, sum);
        return sum;
    }
	
	public static class TreeNode {		
		int val;
		TreeNode left;
		TreeNode right;
		
		TreeNode(int x) {
			val = x;
		}
	}
}

Result

24

Similar Post

1. Sum of all Left Leaves
2. Level Order Traversal of Binary Tree
3. Minimum Distance Between BST Nodes

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