Problem
Find the sum of all left leaves in a given binary tree.
Example:
3 / 9 20 / 15 7
There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.
Solution - Recursiveclass Solution { public int sumOfLeftLeaves(TreeNode root) { if (root == null) return 0; int res = 0; if (root.left != null) { if (root.left.left == null && root.left.right == null) res += root.left.val; else res += sumOfLeftLeaves(root.left); } res += sumOfLeftLeaves(root.right); return res; } }Solution - Iterative
class Solution { public int sumOfLeftLeaves(TreeNode root) { if (root == null) return 0; int res = 0; Dequestack = new ArrayDeque<>(); stack.push(root); while (!stack.isEmpty()) { TreeNode cur = stack.pop(); if (cur.left != null) { if (cur.left.left == null && cur.left.right == null) { res += cur.left.val; } else { stack.push(cur.left); } } if (cur.right != null) { if (cur.right.left != null || cur.right.right != null) { stack.push(cur.right); } } } return res; } }
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