var sumOfLeftLeaves = function (root) {
if (root === null) {
return 0
}
let stack = [root], res = 0
while (stack.length > 0) {
let cur = stack.pop()
if (cur.left && !cur.left.left && !cur.left.right) {
res += cur.left.val
} else if (cur.left) {
stack.push(cur.left)
}
if (cur.right) {
stack.push(cur.right)
}
}
return res
};
Runtime: 60 ms, faster than 40.68% of JavaScript online submissions for Sum of Left Leaves.
Memory Usage: 34.2 MB, less than 100.00% of JavaScript online submissions for Sum of Left Leaves.
func sumOfLeftLeaves(root *TreeNode) int {
if root == nil {
return 0
}
stack := []*TreeNode{root}
var res int
for len(stack) > 0 {
cur := stack[len(stack)-1]
stack = stack[:len(stack)-1]
if cur.Left != nil && cur.Left.Left == nil && cur.Left.Right == nil {
res += cur.Left.Val
} else if cur.Left != nil {
stack = append(stack, cur.Left)
}
if cur.Right != nil {
stack = append(stack, cur.Right)
}
}
return res
}
Runtime: 0 ms, faster than 100.00% of Go online submissions for Sum of Left Leaves.
Memory Usage: 2.6 MB, less than 100.00% of Go online submissions for Sum of Left Leaves.
class Solution:
def sumOfLeftLeaves(self, root: TreeNode) -> int:
if not root:
return 0
stack = [root]
res = 0
while stack:
cur = stack.pop()
if cur.left and not cur.left.left and not cur.left.right:
res += cur.left.val
elif cur.left:
stack.append(cur.left)
if cur.right:
stack.append(cur.right)
return res
Runtime: 44 ms, faster than 26.94% of Python3 online submissions for Sum of Left Leaves.
Memory Usage: 13.8 MB, less than 76.92% of Python3 online submissions for Sum of Left Leaves.
python还能直接用list的变量名，来判断这个list是否还有值。。厉害了😂
是不是一旦为空就都指向一个相同的空数组啊？还是自动被gc了？
递归
class Solution:
def sumOfLeftLeaves(self, root: TreeNode) -> int:
if not root:
return 0
if root and root.left and not root.left.left and not root.left.right:
return root.left.val + self.sumOfLeftLeaves(root.right)
return self.sumOfLeftLeaves(root.left) + self.sumOfLeftLeaves(root.right)
Runtime: 44 ms, faster than 26.94% of Python3 online submissions for Sum of Left Leaves.
Memory Usage: 14.3 MB, less than 7.69% of Python3 online submissions for Sum of Left Leaves.