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SumOfLeftLeaves.js
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SumOfLeftLeaves.js
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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.
*/
// Recursive
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @return {number}
*/
var sumOfLeftLeaves = function(root) {
if(root === null) {
return 0;
}
let result = 0;
if(root.left !== null){
if(!root.left.left && !root.left.right){
result += root.left.val;
} else {
result += sumOfLeftLeaves(root.left);
}
}
if(root.right !== null) {
result += sumOfLeftLeaves(root.right);
}
return result;
};
// Iterative
/**
* @param {TreeNode} root
* @return {number}
*/
var sumOfLeftLeaves = function(root) {
if(root === null) {
return 0;
}
let result = 0, stack = [], node = null;
stack.push(root);
while(stack.length) {
node = new TreeNode(stack.pop());
if(node.left !== null) {
if(node.left.left === null && node.left.right === null) {
result += node.left.val;
} else {
stack.push(node.left);
}
}
if(node.right !== null) {
if(node.right.left !== null || node.right.right !== null) {
stack.push(node.right);
}
}
}
return result;
};