FilesExpand file tree

 master

/

CountCompleteTreeNodes.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

85 lines (72 loc) · 2.1 KB

 master

/

CountCompleteTreeNodes.java

Copy path

Top

File metadata and controls

• Code
• Blame

85 lines (72 loc) · 2.1 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

package leetcode;

/**

* Project Name : Leetcode

* Package Name : leetcode

* File Name : CountCompleteTreeNodes

* Creator : Edward

* Date : Dec, 2017

* Description : 222. Count Complete Tree Nodes

*/

public class CountCompleteTreeNodes {

/**

* Given a complete binary tree, count the number of nodes.

Definition of a complete binary tree from Wikipedia:

In a complete binary tree every level, except possibly the last, is completely filled, and all nodes

in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

3

/ \

9 20

/ \ / \

15 7 1

2^h - 1

time : O(logn * logn)

space : O(n) / O(logn) 不确定

* @param root

* @return

*/

public int countNodes(TreeNode root) {

// int left = helper(root, true);

// int right = helper(root, false);

int left = leftDepth(root);

int right = rightDepth(root);

if (left == right) {

return (1 << left) - 1;

} else {

return 1 + countNodes(root.left) + countNodes(root.right);

}

}

private int leftDepth(TreeNode root) {

int res = 0;

while (root != null) {

root = root.left;

res++;

}

return res;

}

private int rightDepth(TreeNode root) {

int res = 0;

while (root != null) {

root = root.right;

res++;

}

return res;

}

private int helper(TreeNode root, boolean isLeft) {

if (root == null) return 0;

return isLeft ? helper(root.left, isLeft) + 1: helper(root.right, isLeft) + 1;

}

public int countNodes2(TreeNode root) {

if (root == null)

return 0;

TreeNode left = root, right = root;

int height = 0;

while (right != null) {

left = left.left;

right = right.right;

height++;

}

if (left == null)

return (1 << height) - 1;

return 1 + countNodes(root.left) + countNodes(root.right);

}

}