Leetcode: Sum of Left Leaves
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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.
Recursion:
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * int val; 5 * TreeNode left; 6 * TreeNode right; 7 * TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution { 11 public int sumOfLeftLeaves(TreeNode root) { 12 return helper(root, false); 13 } 14 15 public int helper(TreeNode cur, boolean isLeft) { 16 if (cur == null) return 0; 17 if (isLeft && cur.left==null && cur.right==null) return cur.val; 18 return helper(cur.left, true) + helper(cur.right, false); 19 } 20 }
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