FilesExpand file tree

 master

/

CountCompleteTreeNodes.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

106 lines (86 loc) · 2.22 KB

 master

/

CountCompleteTreeNodes.java

Copy path

Top

File metadata and controls

• Code
• Blame

106 lines (86 loc) · 2.22 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

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

/*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.*/

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public class Solution {

public int countNodes(TreeNode root) {

if (root == null) {

return 0;

}

int left = getLeft(root) + 1;

int right = getRight(root) + 1;

if (left == right) {

return (2 << (right - 1)) - 1;

} else {

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

}

}

public int getLeft(TreeNode root) {

if (root == null) {

return 0;

}

int height = 0;

while (root.left != null) {

height++;

root = root.left;

}

return height;

}

public int getRight(TreeNode root) {

if (root == null) {

return 0;

}

int height = 0;

while (root.right != null) {

height++;

root = root.right;

}

return height;

}

}

// Discussion

public class Solution {

public int countNodes(TreeNode root) {

if (root == null)

return 0;

int hLeft = getHeight(root.left);

int hRight = getHeight(root.right);

if (hLeft == hRight)

return (1 << hLeft) + countNodes(root.right);

else

return (1 << hRight) + countNodes(root.left);

}

int getHeight(TreeNode root) {

if (root == null)

return 0;

return 1 + getHeight(root.left);

}

}

// Pochman God

class Solution {

int height(TreeNode root) {

return root == null ? -1 : 1 + height(root.left);

}

public int countNodes(TreeNode root) {

int nodes = 0, h = height(root);

while (root != null) {

if (height(root.right) == h - 1) {

nodes += 1 << h;

root = root.right;

} else {

nodes += 1 << h-1;

root = root.left;

}

h--;

}

return nodes;

}

}