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Leetcode #404 Sum of Left Leaves

leetcode

Posted at 2019-07-02

func sumOfLeftLeaves(_ root: TreeNode?) -> Int {
    var sum = 0
    helper(root, &sum)
    return sum
}

private func helper(_ node: TreeNode?, _ sum: inout Int) {
    if node == nil {
        return
    }
    if node?.left != nil && node?.left?.left == nil && node?.left?.right == nil {
        sum += (node?.left?.val)!
    }
    helper(node?.left, &sum)
    helper(node?.right, &sum)
}

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